Add Maximize and minimize icons (#1172)

Co-authored-by: P-Anurag <anurag.pasupureddi@swimlane.com>

Author: P-Anurag

projects/swimlane/ngx-ui/src/lib/assets/icons/iconfont/fonts/ngx-icon.eot

@@ -503,6 +503,8 @@ $icons: (
   'x-filled': 'eba7',
   'x-small': 'eba8',
   'x': 'eba9',
+  'maximize': 'ebaa',
+  'minimize': 'ebab',
 );
 
 @function unicode($str) {