Update readme files

Author: sergepilipchuk

README.md

@@ -3,6 +3,26 @@
 [![](https://img.shields.io/badge/Open_in_DevExpress_Support_Center-FF7200?style=flat-square&logo=DevExpress&logoColor=white)](https://supportcenter.devexpress.com/ticket/details/T945799)
 [![](https://img.shields.io/badge/📖_How_to_use_DevExpress_Examples-e9f6fc?style=flat-square)](https://docs.devexpress.com/GeneralInformation/403183)
 <!-- default badges end -->
-# Getting Started with DevExtreme DropDownButton
+# DevExtreme DropDownButton - Getting Started 
 
-This repository stores the source code for the [Getting Started with DropDownButton](https://js.devexpress.com/Documentation/Guide/UI_Components/DropDownButton/Getting_Started_with_DropDownButton/) tutorial.
+This repository stores the code examples of the DropDownButton component for the [Getting Started with DropDownButton](https://js.devexpress.com/Documentation/Guide/UI_Components/DropDownButton/Getting_Started_with_DropDownButton/) tutorial. The DropDownButton combines the functionality of a button and a drop-down menu. This tutorial describes how to configure a DropDownButton that logs user clicks in the browser console.
+
+<div align="center"><img src="./dropdownbutton.png" /></div>
+
+## Files to Review
+
+- **Angular**
+    - [app.component.html](angular/src/app/app.component.html)
+    - [app.component.ts](angular/src/app/app.component.ts)
+- **jQuery**
+    - [index.js](jquery/src/index.js)
+- **React**
+    - [App.js](react/src/App.js)
+- **Vue**
+    - [App.vue](vue/src/App.vue)
+
+## Documentation
+
+- [Getting Started with DropDownButton](https://js.devexpress.com/Documentation/Guide/UI_Components/DropDownButton/Getting_Started_with_DropDownButton/)
+
+- [DropDownButton - API Reference](https://js.devexpress.com/Documentation/ApiReference/UI_Components/dxDropDownButton/)

angular/README.md

@@ -1,6 +1,6 @@
-# Getting Started with DevExtreme Angular DropDownButton
+# DevExtreme Angular DropDownButton - Getting Started
 
-This repository stores Angular source code for the [Getting Started with DropDownButton](https://js.devexpress.com/Documentation/Guide/UI_Components/DropDownButton/Getting_Started_with_DropDownButton/) tutorial.
+This repository stores the code examples of the Angular DropDownButton component for the [Getting Started with DropDownButton](https://js.devexpress.com/Documentation/Guide/UI_Components/DropDownButton/Getting_Started_with_DropDownButton/) tutorial. The DropDownButton combines the functionality of a button and a drop-down menu. This tutorial describes how to configure a DropDownButton that logs user clicks in the browser console.
 
 This project was generated with [Angular CLI](https://github.com/angular/angular-cli) version 10.2.0.
 
@@ -18,12 +18,12 @@ Run `ng build` to build the project. The build artifacts will be stored in the `
 
 ## Running unit tests
 
-Run `ng test` to execute the unit tests via [Karma](https://karma-runner.github.io).
+Run `ng test` to execute unit tests using [Karma](https://karma-runner.github.io).
 
 ## Running end-to-end tests
 
-Run `ng e2e` to execute the end-to-end tests via [Protractor](http://www.protractortest.org/).
+Run `ng e2e` to execute end-to-end tests using [Protractor](http://www.protractortest.org/).
 
 ## Further help
 
-To get more help on the Angular CLI use `ng help` or go check out the [Angular CLI Overview and Command Reference](https://angular.io/cli) page.
+To get more help on the Angular CLI, use `ng help` or review the [Angular CLI Overview and Command Reference](https://angular.io/cli) page.

dropdownbutton.png

@@ -1,5 +1,24 @@
-# Getting Started with DevExtreme jQuery DropDownButton
+# DevExtreme jQuery DropDownButton - Getting Started
 
-This repository stores jQuery source code for the [Getting Started with DropDownButton](https://js.devexpress.com/Documentation/Guide/UI_Components/DropDownButton/Getting_Started_with_DropDownButton/) tutorial.
+This repository stores the code examples of the jQuery DropDownButton component for the [Getting Started with DropDownButton](https://js.devexpress.com/Documentation/Guide/UI_Components/DropDownButton/Getting_Started_with_DropDownButton/) tutorial. The DropDownButton combines the functionality of a button and a drop-down menu. This tutorial describes how to configure a DropDownButton that logs user clicks in the browser console.
 
-To launch the project, open `index.html` with your browser.
+## Installation
+
+Download the example and use NPM to install required libraries.
+
+```
+npm install
+```
+
+## Development server
+
+Run the `npm run start` command to run the development server. Use the following link to check the example:
+```
+http://localhost:3000/src/index.html
+```
+
+## Further help
+
+You can learn more about jQuery API in the [jQuery documentation](https://api.jquery.com/).
+
+To get more help on DevExtreme, submit an issue on [GitHub](https://github.com/DevExpress/devextreme/issues) or [Support Center](https://www.devexpress.com/Support/Center/Question/Create).

jquery/README.md

@@ -1,6 +1,6 @@
-# Getting Started with DevExtreme React DropDownButton
+# DevExtreme React DropDownButton - Getting Started
 
-This repository stores React source code for the [Getting Started with DropDownButton](https://js.devexpress.com/Documentation/Guide/UI_Components/DropDownButton/Getting_Started_with_DropDownButton/) tutorial.
+This repository stores the code examples of the React DropDownButton component for the [Getting Started with DropDownButton](https://js.devexpress.com/Documentation/Guide/UI_Components/DropDownButton/Getting_Started_with_DropDownButton/) tutorial. The DropDownButton combines the functionality of a button and a drop-down menu. This tutorial describes how to configure a DropDownButton that logs user clicks in the browser console.
 
 This project was bootstrapped with [Create React App](https://github.com/facebook/create-react-app).
 

react/README.md

@@ -1,6 +1,6 @@
-# Getting Started with DevExtreme Vue DropDownButton
+# DevExtreme Vue DropDownButton - Getting Started 
 
-This repository stores Vue source code for the [Getting Started with DropDownButton](https://js.devexpress.com/Documentation/Guide/UI_Components/DropDownButton/Getting_Started_with_DropDownButton/) tutorial.
+This repository stores the code examples of the Vue DropDownButton component for the [Getting Started with DropDownButton](https://js.devexpress.com/Documentation/Guide/UI_Components/DropDownButton/Getting_Started_with_DropDownButton/) tutorial. The DropDownButton combines the functionality of a button and a drop-down menu. This tutorial describes how to configure a DropDownButton that logs user clicks in the browser console.
 
 ## Project setup
 ```