feat: add AI command suggestions extension for Tiptap editor

- Implemented Commands plugin to handle command suggestions triggered by '@' character.
- Created suggestion configuration to filter and render command items.
- Added various command items including date, time, formatting, templates, and task management commands.
- Introduced CSS styles for the Tiptap editor to enhance UI.
- Configured TypeScript settings and Vite build for the project.

mod.ts

@@ -0,0 +1,2 @@
+import './src/index.css'
+export * from './src/md-editor.ts';