docs(form-controls): add gradient-picker (#1599)

Author: jdegand

README.md

@@ -1436,6 +1436,7 @@ Current Angular version: [![npm version](https://badge.fury.io/js/%40angular%2Fc
 * [ngx-input-color](https://github.com/mr-samani/ngx-input-color) - `ngx-input-color` and `ngx-input-gradient` are powerful, customizable Angular components for color and gradient picking. They support multiple color formats, real-time preview, inline and input modes, and seamless integration with Angular forms.
 * [ngx-morse](https://github.com/monkeyscript/ngx-morse) - A simple morse code encoder and decoder for Angular.
 * [ngxsmk-tel-input](https://github.com/toozuuu/ngxsmk-tel-input) - An Angular telephone input component with country dropdown, flags, and robust validation/formatting.
+* [gradient-picker](https://github.com/acrodata/gradient-picker) - A powerful and beautiful gradient picker.
 
 ### JSON Forms