Add Yarn installation description

Author: valery1707

README.md

@@ -21,6 +21,12 @@ npm install angular-file-upload
 ```
 You could find this module in npm like [_angular file upload_](https://www.npmjs.com/search?q=angular-file-upload).
 
+### Yarn [![npm](https://img.shields.io/npm/v/angular-file-upload.svg)](https://www.npmjs.com/search?q=angular-file-upload)
+```
+yarn add --exact angular-file-upload
+```
+You could find this module in yarn like [_angular file upload_](https://yarnpkg.com/en/packages?q=angular-file-upload).
+
 ### Module Dependency
 
 Add `'angularFileUpload'` to your module declaration: