feat(editor): support preview mode in code block (#11805)

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

- **New Features**
  - Introduced a preview mode for code blocks, allowing users to toggle between code and rendered previews (e.g., HTML output) directly within the editor.
  - Added a preview toggle button to the code block toolbar for supported languages.
  - Enabled dynamic rendering of code block previews using a shared WebContainer, allowing live HTML previews in an embedded iframe.
  - Added HTML preview support with loading and error states for enhanced user feedback.
  - Integrated the preview feature as a view extension provider for seamless framework support.

- **Bug Fixes**
  - Improved toolbar layout and button alignment for a cleaner user interface.

- **Tests**
  - Added end-to-end tests to verify the new code block preview functionality and language switching behavior.

- **Chores**
  - Updated development server configuration to include enhanced security headers.
  - Added a new runtime dependency for WebContainer support.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/frontend/core/package.json

@@ -39,6 +39,7 @@
     "@toeverything/pdf-viewer": "^0.1.1",
     "@toeverything/theme": "^1.1.14",
     "@vanilla-extract/dynamic": "^2.1.2",
+    "@webcontainer/api": "^1.6.1",
     "animejs": "^4.0.0",
     "bytes": "^3.1.2",
     "clsx": "^2.1.1",