Support custom icons in custom menu popover components Edit menu item; Add custom menu item. Update mixins to handle sizing for image icons.

ui-ngx/src/scss/mixins.scss

@@ -26,6 +26,10 @@
     width: #{$size}px;
     height: #{$size}px;
   }
+  img {
+    width: #{$size}px;
+    height: #{$size}px;
+  }
 }
 
 @mixin tb-mat-icon-button-size($size) {