feat(editor): add experimental feature adapter panel to AFFiNE canary (#12489)

Closes: [BS-2539](https://linear.app/affine-design/issue/BS-2539/为-affine-添加-ef，并且支持在-affine-预览对应的功能)

> [!warning]
> This feature is only available in the canary build and is intended for debugging purposes.

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

- **New Features**
  - Introduced an "Adapter Panel" feature with a new sidebar tab for previewing document content in multiple formats (Markdown, PlainText, HTML, Snapshot), controllable via a feature flag.
  - Added a fully integrated adapter panel component with reactive UI elements for selecting adapters, toggling HTML preview modes, and updating content.
  - Provided a customizable adapter panel for both main app and playground environments, supporting content transformation pipelines and export previews.
  - Enabled seamless toggling and live updating of adapter panel content through intuitive menus and controls.

- **Localization**
  - Added English translations and descriptive settings for the Adapter Panel feature.

- **Chores**
  - Added new package and workspace dependencies along with TypeScript project references to support the Adapter Panel modules and components.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/frontend/core/src/modules/feature-flag/constant.ts

@@ -327,6 +327,15 @@ export const AFFINE_FLAGS = {
     configurable: isCanaryBuild,
     defaultState: true,
   },
+  enable_adapter_panel: {
+    category: 'affine',
+    displayName:
+      'com.affine.settings.workspace.experimental-features.enable-adapter-panel.name',
+    description:
+      'com.affine.settings.workspace.experimental-features.enable-adapter-panel.description',
+    configurable: isCanaryBuild,
+    defaultState: false,
+  },
 } satisfies { [key in string]: FlagInfo };
 
 // oxlint-disable-next-line no-redeclare