Docs: add installation and usage

Author: aichbauer

README.md

@@ -2,6 +2,33 @@
 
 > Check if a git remote repository exists
 
+## Installation
+
+```sh
+$ npm i is-git-remote --save
+```
+
+or
+
+```sh
+$ yarn add is-git-remote
+```
+
+## Usage
+
+```js
+const isGitRemote = require('is-git-remote'); // import isGitRemote from 'is-git-remote'
+
+countGitTags('www.github.com/username/repo-that-exists'); // => true
+
+countGitTags('https://www.github.com/username/repo-that-exists'); // => true
+
+countGitTags('username/repo-that-exists', 'bitbucket.com'); // => true
+
+// automatically checks github if no host is provided
+countGitTags('username/repo-that-not-exists'); // => false
+```
+
 ## LICENSE
 
 MIT © Lukas Aichbauer