feat(editor): support footnote adapter (#9844)

[BS-2373](https://linear.app/affine-design/issue/BS-2373/适配-footnote-adapter)

blocksuite/affine/shared/src/adapters/index.ts

@@ -20,6 +20,7 @@ export {
   BlockMarkdownAdapterExtension,
   type BlockMarkdownAdapterMatcher,
   BlockMarkdownAdapterMatcherIdentifier,
+  FOOTNOTE_DEFINITION_PREFIX,
   InlineDeltaToMarkdownAdapterExtension,
   type InlineDeltaToMarkdownAdapterMatcher,
   InlineDeltaToMarkdownAdapterMatcherIdentifier,

blocksuite/affine/shared/src/adapters/markdown/gfm.ts

@@ -4,9 +4,12 @@ MIT License
 Copyright (c) 2020 Titus Wormer <tituswormer@gmail.com>
 
 mdast-util-gfm-autolink-literal is from markdown only.
-mdast-util-gfm-footnote is not included.
 */
 import { gfmAutolinkLiteralFromMarkdown } from 'mdast-util-gfm-autolink-literal';
+import {
+  gfmFootnoteFromMarkdown,
+  gfmFootnoteToMarkdown,
+} from 'mdast-util-gfm-footnote';
 import {
   gfmStrikethroughFromMarkdown,
   gfmStrikethroughToMarkdown,
@@ -17,6 +20,7 @@ import {
   gfmTaskListItemToMarkdown,
 } from 'mdast-util-gfm-task-list-item';
 import { gfmAutolinkLiteral } from 'micromark-extension-gfm-autolink-literal';
+import { gfmFootnote } from 'micromark-extension-gfm-footnote';
 import { gfmStrikethrough } from 'micromark-extension-gfm-strikethrough';
 import { gfmTable } from 'micromark-extension-gfm-table';
 import { gfmTaskListItem } from 'micromark-extension-gfm-task-list-item';
@@ -29,6 +33,7 @@ export function gfm() {
     gfmStrikethrough(),
     gfmTable(),
     gfmTaskListItem(),
+    gfmFootnote(),
   ]);
 }
 
@@ -38,6 +43,7 @@ function gfmFromMarkdown() {
     gfmTableFromMarkdown(),
     gfmTaskListItemFromMarkdown(),
     gfmAutolinkLiteralFromMarkdown(),
+    gfmFootnoteFromMarkdown(),
   ];
 }
 
@@ -47,6 +53,7 @@ function gfmToMarkdown() {
       gfmStrikethroughToMarkdown(),
       gfmTableToMarkdown(),
       gfmTaskListItemToMarkdown(),
+      gfmFootnoteToMarkdown(),
     ],
   };
 }

blocksuite/affine/shared/src/adapters/markdown/type.ts

@@ -15,3 +15,5 @@ export const isMarkdownAST = (node: unknown): node is MarkdownAST =>
   !Array.isArray(node) &&
   'type' in (node as object) &&
   (node as MarkdownAST).type !== undefined;
+
+export const FOOTNOTE_DEFINITION_PREFIX = 'footnoteDefinition:';