feat(editor): add experimental feature citation (#11984)

Closes: [BS-3122](https://linear.app/affine-design/issue/BS-3122/footnote-definition-adapter-适配)
Closes: [BS-3123](https://linear.app/affine-design/issue/BS-3123/几个-block-card-view-适配-footnote-态)

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

- **New Features**
  - Introduced a new citation card component and web element for displaying citations.
  - Added support for citation-style rendering in attachment, bookmark, and linked document blocks.
  - Enabled citation parsing from footnote definitions in markdown for attachments, bookmarks, and linked docs.
  - Added a feature flag to enable or disable citation features.
  - Provided new toolbar logic to disable downloads for citation-style attachments.

- **Improvements**
  - Updated block models and properties to support citation identifiers.
  - Added localization and settings for the citation experimental feature.
  - Enhanced markdown adapters to recognize and process citation footnotes.
  - Included new constants and styles for citation card display.

- **Bug Fixes**
  - Ensured readonly state is respected in block interactions and rendering for citation blocks.

- **Documentation**
  - Added exports and effects for new citation components and features.

- **Tests**
  - Updated snapshots to include citation-related properties in block data.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

blocksuite/affine/blocks/paragraph/src/adapters/markdown.ts

@@ -9,6 +9,15 @@ import type { DeltaInsert } from '@blocksuite/store';
 import { nanoid } from '@blocksuite/store';
 import type { Heading } from 'mdast';
 
+/**
+ * Extend the HeadingData type to include the collapsed property
+ */
+declare module 'mdast' {
+  interface HeadingData {
+    collapsed?: boolean;
+  }
+}
+
 const PARAGRAPH_MDAST_TYPE = new Set(['paragraph', 'heading', 'blockquote']);
 
 const isParagraphMDASTType = (node: MarkdownAST) =>
@@ -46,6 +55,7 @@ export const paragraphBlockMarkdownAdapterMatcher: BlockMarkdownAdapterMatcher =
             break;
           }
           case 'heading': {
+            const isCollapsed = !!o.node.data?.collapsed;
             walkerContext
               .openNode(
                 {
@@ -54,6 +64,7 @@ export const paragraphBlockMarkdownAdapterMatcher: BlockMarkdownAdapterMatcher =
                   flavour: 'affine:paragraph',
                   props: {
                     type: `h${o.node.depth}`,
+                    collapsed: isCollapsed,
                     text: {
                       '$blocksuite:internal:text$': true,
                       delta: deltaConverter.astToDelta(o.node),