feat: add syntax highlighting and enhance document editing features

- Import GitHub dark theme for highlight.js in main.ts
- Pass slug prop to VisualEditor in DocumentView.vue for version and normal editing modes
- Update Vite configuration to increase maximum cache size and add media proxy
- Add new dependencies for Tiptap extensions and highlight.js in package.json and package-lock.json

frontend/src/main.ts

@@ -3,6 +3,7 @@ import { createPinia } from 'pinia'
 import { router } from '@/router'
 import App from '@/App.vue'
 import '@/assets/main.css'
+import 'highlight.js/styles/github-dark.css'
 
 const app = createApp(App)
 app.use(createPinia())