markdown preview: highlight code blocks (#9087)

![image](https://github.com/zed-industries/zed/assets/53836821/e20acd87-9680-4e1c-818d-7ae900bf0e31)

Release Notes:

- Added syntax highlighting to code blocks in markdown preview
- Fixed scroll position in markdown preview when editing a markdown file
(#9208)

crates/auto_update/src/auto_update.rs

@@ -229,6 +229,7 @@ fn view_release_notes_locally(workspace: &mut Workspace, cx: &mut ViewContext<Wo
                             buffer.update(cx, |buffer, cx| {
                                 buffer.edit([(0..0, body.release_notes)], None, cx)
                             });
+                            let language_registry = project.read(cx).languages().clone();
 
                             let buffer = cx.new_model(|cx| MultiBuffer::singleton(buffer, cx));
 
@@ -240,6 +241,7 @@ fn view_release_notes_locally(workspace: &mut Workspace, cx: &mut ViewContext<Wo
                                 editor,
                                 workspace_handle,
                                 Some(tab_description),
+                                language_registry,
                                 cx,
                             );
                             workspace.add_item_to_active_pane(Box::new(view.clone()), cx);