refactor(editor): extract widgets (#12304)

<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit

- **New Features**
  - Introduced two new widgets: Edgeless Dragging Area and Note Slicer, now available for use.
  - Added extension support for these widgets, enabling enhanced interaction and integration within the application.

- **Chores**
  - Updated package configurations and workspace settings to include the new widgets and their dependencies.
  - Added project references and configuration files to support modular development and build processes.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

blocksuite/affine/widgets/note-slicer/src/effects.ts

@@ -0,0 +1,5 @@
+import { NOTE_SLICER_WIDGET, NoteSlicer } from './note-slicer';
+
+export function effects() {
+  customElements.define(NOTE_SLICER_WIDGET, NoteSlicer);
+}