Add icon color to custom button

lib/src/models/themes/quill_custom_button.dart

@@ -3,6 +3,7 @@ import 'package:flutter/material.dart';
 class QuillCustomButton {
   const QuillCustomButton({
     this.icon,
+    this.iconColor,
     this.onTap,
     this.tooltip,
   });
@@ -10,6 +11,9 @@ class QuillCustomButton {
   ///The icon widget
   final IconData? icon;
 
+  ///The icon color;
+  final Color? iconColor;
+  
   ///The function when the icon is tapped
   final VoidCallback? onTap;