doc: update screens api doc according to new pattern.

Author: narekhovhannisyan

docs/project-data-api/SCREENS_API.md

@@ -1,45 +1,45 @@
-## Screens API 
+# Screens API
 
-  * [Getters](#getters)
+## Table of Contents
+
+- [Screens API](#screens-api)
+  - [Table of Contents](#table-of-contents)
+  - [Getters](#getters)
     - [Get areas](#get-areas)
     - [Get area](#get-area)
     - [Calculate screen duration](#calculate-screen-duration)
     - [Get max possible duration](#get-max-possible-duration)
-  * [Setters](#setters)
+  - [Setters](#setters)
     - [Set duration](#set-duration)
     - [Toggle icon position](#toggle-icon-position)
     - [Set lower third settings](#set-lower-third-settings)
+  - [Return project data](#return-project-data)
+  - [Save](#save)
 
 ## Getters
 
 ### Get areas
 
-Maps through `areas` array and adds it's methods.
+Gets areas for current screen.
 
 ```js
-const firstScreen = projectDataInstance.getScreen(0)
-
-firstScreen.getAreas() // array of areas object
+console.log(projectDataInstance.getScreen(0).getAreas()) // array of areas object
 ```
 
 ### Get area
 
-Gets area with given `index`.
+Gets area with given `index` for current screen.
 
 ```js
-const firstScreen = projectDataInstance.getScreen(0)
-
-firstScreen.getArea(0) // gets area with index 0 (first area)
+console.log(projectDataInstance.getScreen(0).getArea(0)) // gets area with index 0 (first area)
 ```
 
 ### Calculate screen duration
 
 Calculates screen duration. It's useful when there is need to manually set screen duration.
 
 ```js
-const screen = projectDataInstance.getScreen(0)
-
-screen.calculateScreenDuration()
+console.log(projectDataInstance.getScreen(0).calculateScreenDuration())
 ```
 
 ### Get max possible duration
@@ -48,14 +48,12 @@ Filters areas to find only video ones. Checks if count of video areas is more th
  Otherwise returns `maxDuration` if there is one, or `duration`.
 
 ```js
-const screen = projectDataInstance.getScreen(0)
-
-screen.getMaxPossibleDuration()
+console.log(projectDataInstance.getScreen(0).getMaxPossibleDuration())
 ```
 
 ## Setters
 
-All the setters of screen instance can be called with chaining.
+All the setters of screen instance can be called in chain.
 
 ### Set duration
 
@@ -64,16 +62,11 @@ then also throws error. Otherwise sets given value.
 
 ```js
 Renderforest.getProjectData(15220886)
-  .then((projectDataInstance) => {
-    const screen = projectDataInstance.getScreen(0)
-    // these steps are not necessary
-    const screenDuration = screen.calculateScreenDuration()
-    console.log(screenDuration)
-    const maxDuration = screen.getMaxPossibleDuration()
-    console.log(maxDuration)
-
-    return screen.setDuration(5)
-  })
+  .then((projectDataInstance) => 
+    projectDataInstance.getScreen(0)
+      .setDuration(5)
+      .save()
+  )
 ```
 
 ### Toggle icon position
@@ -82,12 +75,11 @@ If screen does not have icon adjustment, then throws error. Otherwise toggles ic
 
 ```js
 Renderforest.getProjectData(15220886)
-  .then((projectDataInstance) => {
-    const screen = projectDataInstance.getScreen(0)
-
-    return screen.setDuration(5)
+  .then((projectDataInstance) => 
+    projectDataInstance.setDuration(5)
       .toggleIconPosition()
-  })
+      .save()
+  )
 ``` 
 
 [See screen duration and toggle icon position adjustment example](/samples/project-data/screen-duration-and-icon-toggle.js)
@@ -99,17 +91,40 @@ Otherwise sets `start` and `duration` params for lower third settings.
 
 ```js
 Renderforest.getProjectData(15220886)
-  .then((projectDataInstance) => {
-    const screen = projectDataInstance.getScreen(0)
+  .then((projectDataInstance) => 
+      projectDataInstance.getScreen(0)
+        .setLowerThirdSettings(2, 5)
+        .save()
+  )
+```
+
+[See lower third settings adjustment example](/samples/project-data/lower-third-settings.js)
+
+## Return project data
 
-    screen
-      .setLowerThirdSettings(2, 5)
+For project data manipulation sometimes there is need to step back from
+area object to project data for further development. 
 
-    return projectDataInstance.save()
-  })
-  .catch(console.error)
+```js
+projectDataInstance.getScreen(0)
+  .setLowerThirdSettings(2, 5)
+  .returnProjectData()
+  .getScreen(1)
+  .setDuration(8)
 ```
 
-[See lower third settings adjustment example](/samples/project-data/lower-third-settings.js)
+## Save
+
+Save method works with the same logic as the project data one. 
+From the hood it steps back project data then calls save method. 
+
+```js
+projectDataInstance.getScreen(0)
+  .setLowerThirdSettings(2, 5)
+  .returnProjectData()
+  .getScreen(1)
+  .setDuration(8)
+  .save()
+```
 
 **[⬆ back to the top](#screens-api)**