Support alternative text selection

Author: micahmo

lib/src/format_markdown.dart

@@ -11,6 +11,9 @@ class FormatMarkdown {
     /// String to convert
     String data,
 
+    /// An alternate data source on which to perform formatting
+    String? alternateData,
+
     /// Start index when converting part of [data]
     int fromIndex,
 
@@ -71,7 +74,7 @@ class FormatMarkdown {
         break;
       case MarkdownType.blockquote:
         var index = 0;
-        final splitedData = data.substring(fromIndex, toIndex).split('\n');
+        final splitedData = (alternateData ?? data.substring(fromIndex, toIndex)).split('\n');
         changedData = splitedData.map((value) {
           index++;
           return index == splitedData.length ? '> $value' : '> $value\n';

lib/src/markdown_toolbar.dart

@@ -33,6 +33,9 @@ class MarkdownToolbar extends StatelessWidget {
   /// Allows overriding tap actions for each [MarkdownType]
   final Map<MarkdownType, void Function()>? customTapActions;
 
+  /// A function which allows the widget's parent to provide an alternate text selection
+  final String? Function()? getAlternativeSelection;
+
   /// Constructor for [MarkdownToolbar]
   const MarkdownToolbar({
     super.key,
@@ -43,6 +46,7 @@ class MarkdownToolbar extends StatelessWidget {
     this.customImageButtonAction,
     this.imageIsLoading = false,
     this.customTapActions,
+    this.getAlternativeSelection,
   });
 
   @override
@@ -223,6 +227,7 @@ class MarkdownToolbar extends StatelessWidget {
     ResultMarkdown result = FormatMarkdown.convertToMarkdown(
       type,
       controller.text,
+      getAlternativeSelection?.call(),
       fromIndex,
       toIndex,
       titleSize: titleSize,