content: Add ZulipRenderedContent for rendering zulip HTML

Author: sm-sayedi

lib/widgets/content.dart

@@ -305,6 +305,20 @@ class MessageContent extends StatelessWidget {
   }
 }
 
+class ZulipRenderedContent extends StatelessWidget {
+  const ZulipRenderedContent(this.content, {super.key, this.style});
+
+  final ZulipContent content;
+  final TextStyle? style;
+
+  @override
+  Widget build(BuildContext context) {
+    return DefaultTextStyle(
+      style: ContentTheme.of(context).textStylePlainParagraph.merge(style),
+      child: BlockContentList(nodes: content.nodes));
+  }
+}
+
 class InheritedMessage extends InheritedWidget {
   const InheritedMessage({super.key, required this.message, required super.child});
 

lib/widgets/message_list.dart

@@ -2328,9 +2328,7 @@ class OutboxMessageWithPossibleSender extends StatelessWidget {
     // This is adapted from [MessageContent].
     // TODO(#576): Offer InheritedMessage ancestor once we are ready
     //   to support local echoing images and lightbox.
-    Widget content = DefaultTextStyle(
-      style: ContentTheme.of(context).textStylePlainParagraph,
-      child: BlockContentList(nodes: item.content.nodes));
+    Widget content = ZulipRenderedContent(item.content);
 
     switch (message.state) {
       case OutboxMessageState.hidden: