feat(editor): viewport overlay widget extension (#12035)

Closes: BS-3360

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

- **New Features**
  - Introduced a new viewport overlay widget, making it available as part of the workspace and enabling its integration into supported pages.

- **Refactor**
  - Updated internal imports and exports to utilize the new viewport overlay widget package.
  - Streamlined widget registration and extension mechanisms for improved modularity.

- **Chores**
  - Added configuration and project references to support the new viewport overlay widget package in the build system.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

blocksuite/affine/all/package.json

@@ -64,6 +64,7 @@
     "@blocksuite/affine-widget-scroll-anchoring": "workspace:*",
     "@blocksuite/affine-widget-slash-menu": "workspace:*",
     "@blocksuite/affine-widget-toolbar": "workspace:*",
+    "@blocksuite/affine-widget-viewport-overlay": "workspace:*",
     "@blocksuite/data-view": "workspace:*",
     "@blocksuite/global": "workspace:*",
     "@blocksuite/std": "workspace:*",
@@ -184,6 +185,8 @@
     "./widgets/toolbar/view": "./src/widgets/toolbar/view.ts",
     "./widgets/keyboard-toolbar": "./src/widgets/keyboard-toolbar/index.ts",
     "./widgets/keyboard-toolbar/view": "./src/widgets/keyboard-toolbar/view.ts",
+    "./widgets/viewport-overlay": "./src/widgets/viewport-overlay/index.ts",
+    "./widgets/viewport-overlay/view": "./src/widgets/viewport-overlay/view.ts",
     "./fragments/doc-title": "./src/fragments/doc-title.ts",
     "./fragments/frame-panel": "./src/fragments/frame-panel.ts",
     "./fragments/outline": "./src/fragments/outline.ts",