feat: refactor logic for converting color string to Color in backgrou…

…nd_color_mixin.dart (#538)

lib/src/editor/block_component/base_component/background_color_mixin.dart

@@ -1,6 +1,14 @@
 import 'package:appflowy_editor/appflowy_editor.dart';
 import 'package:flutter/material.dart';
 
+/// If you want to customize the logic of how to convert a color string to a
+///   [Color], you can set this variable.
+typedef BlockComponentBackgroundColorDecorator = Color? Function(
+  Node node,
+  String colorString,
+);
+BlockComponentBackgroundColorDecorator? blockComponentBackgroundColorDecorator;
+
 mixin BlockComponentBackgroundColorMixin {
   Node get node;
 
@@ -10,6 +18,12 @@ mixin BlockComponentBackgroundColorMixin {
     if (colorString == null) {
       return Colors.transparent;
     }
-    return colorString.tryToColor() ?? Colors.transparent;
+
+    return blockComponentBackgroundColorDecorator?.call(
+          node,
+          colorString,
+        ) ??
+        colorString.tryToColor() ??
+        Colors.transparent;
   }
 }