feat: use external web colors and more bbcode parsing

This commit moved pre-defined web colors and related color utilities
to external package `dart_bbcode_web_colors` because multiple packages
in this project rely on the same functionality.

Besides, update upstream code to get more bbcode parsing support, till
now most frequently used bbcode tags can be recognized and parsed into
quill delta.

Author: realth000

.gitmodules

@@ -7,3 +7,6 @@
 [submodule "packages/dart_bbcode_parser"]
 	path = packages/dart_bbcode_parser
 	url = https://github.com/realth000/dart_bbcode_parser.git
+[submodule "packages/dart_bbcode_web_colors"]
+	path = packages/dart_bbcode_web_colors
+	url = git@github.com:realth000/dart_bbcode_web_colors.git

lib/utils/html/css_parser.dart

@@ -1,9 +1,7 @@
 import 'dart:ui';
 
+import 'package:dart_bbcode_web_colors/dart_bbcode_web_colors.dart';
 import 'package:tsdm_client/shared/models/models.dart';
-import 'package:tsdm_client/utils/html/web_colors.dart';
-
-final _colorRe = RegExp(r'^(#)?[0-9a-fA-F]{1,6}$');
 
 /// Parse a [String] of css to [CssTypes].
 ///
@@ -60,44 +58,3 @@ FontWeight? _parseFontWeight(String data) {
 
   return (cssPart.substring(0, separateIndex), cssPart.substring(separateIndex + 1));
 }
-
-/// Extension to convert nullable string to [Color].
-extension StringToColorExt on String? {
-  /// Parse nullable color string to [Color].
-  ///
-  /// * If `this` is null, return null.
-  /// * Parse `this` in style `#COLOR_VALUE` or `COLOR_NAME` where COLOR_NAME is
-  ///   hit in [WebColors].
-  Color? toColor() {
-    int? colorValue;
-    // Parse as color value.
-    if (this != null && _colorRe.hasMatch(this!)) {
-      if (this!.startsWith('#')) {
-        if (this!.length == 4) {
-          // #abc format short hand for #aabbcc.
-          colorValue = int.tryParse(
-            '${this![1]}${this![1]}${this![2]}'
-            '${this![2]}${this![3]}${this![3]}',
-            radix: 16,
-          );
-        } else {
-          // Normal #aabbcc format.
-          colorValue = int.tryParse(this!.substring(1), radix: 16);
-        }
-      } else {
-        colorValue = int.tryParse(this!, radix: 16);
-      }
-    }
-    if (colorValue != null) {
-      colorValue += 0xFF000000;
-      return Color(colorValue);
-    } else {
-      // If color not in format #aabcc, try parse as color name.
-      final webColor = WebColors.fromString(this);
-      if (webColor.isValid) {
-        return webColor.color;
-      }
-    }
-    return null;
-  }
-}

lib/utils/html/html_muncher.dart

@@ -1,4 +1,5 @@
 import 'package:collection/collection.dart';
+import 'package:dart_bbcode_web_colors/dart_bbcode_web_colors.dart';
 import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';
 import 'package:tsdm_client/constants/layout.dart';