style: Improve markdown editor styling and functionality

- Update dark mode button icon and styling
- Add styling for new collection button
- Apply default iframe styles in preview pane
- Adjust vertical divider height in header buttons
- Improve handling of JSX-like attributes in markdown
- Add support for new collection functionality
- Refine file loading logic in view mode
- Improve dark mode toggle icon and integration
- Update UI for edit/view mode toggle button

config.yaml

@@ -23,6 +23,9 @@ collections:
   7madah:
     path: collections/7madah
     description: 'User-created collection: 7madah'
+  tech:
+    path: collections/tech
+    description: 'User-created collection: tech'
 server:
   host: localhost
   port: 8004