Related to: [BS-3559](https://linear.app/affine-design/issue/BS-3559/ui-%E5%9B%BE%E7%89%87-loading-%E5%8F%98%E9%87%8F%E6%9B%B4%E6%96%B0)
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## Summary by CodeRabbit
- **Style**
- Improved the appearance of image loading indicators by updating background and ring colors for a more consistent visual experience.
- **New Features**
- Added customization options for the loading icon's ring color.
- **Chores**
- Updated the "@toeverything/theme" dependency to version ^1.1.15 across multiple packages for improved consistency and compatibility.
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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.
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fundon