Add Markdown source highlighting (#173)

src/lib/types.ts

@@ -129,6 +129,7 @@ export interface AppConfig {
   ai_model: string;
   ai_writing_style: string | null;
   default_view_mode: boolean;
+  new_notes_in_source_mode: boolean;
   show_tray_icon: boolean;
   close_to_tray: boolean;
   enable_wiki_links: boolean;