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/widgets/viewport-overlay/package.json

@@ -0,0 +1,40 @@
+{
+  "name": "@blocksuite/affine-widget-viewport-overlay",
+  "description": "Affine viewport overlay widget.",
+  "type": "module",
+  "scripts": {
+    "build": "tsc"
+  },
+  "sideEffects": false,
+  "keywords": [],
+  "author": "toeverything",
+  "license": "MIT",
+  "dependencies": {
+    "@blocksuite/affine-components": "workspace:*",
+    "@blocksuite/affine-ext-loader": "workspace:*",
+    "@blocksuite/affine-model": "workspace:*",
+    "@blocksuite/affine-shared": "workspace:*",
+    "@blocksuite/global": "workspace:*",
+    "@blocksuite/icons": "^2.2.12",
+    "@blocksuite/std": "workspace:*",
+    "@floating-ui/dom": "^1.6.13",
+    "@preact/signals-core": "^1.8.0",
+    "@toeverything/theme": "^1.1.12",
+    "@types/lodash-es": "^4.17.12",
+    "lit": "^3.2.0",
+    "lodash-es": "^4.17.21",
+    "rxjs": "^7.8.1"
+  },
+  "exports": {
+    ".": "./src/index.ts",
+    "./effects": "./src/effects.ts",
+    "./view": "./src/view.ts"
+  },
+  "files": [
+    "src",
+    "dist",
+    "!src/__tests__",
+    "!dist/__tests__"
+  ],
+  "version": "0.21.0"
+}