feat(core): moving in affine-reader doc parsers (#12840)

fix AI-191

#### PR Dependency Tree


* **PR #12840** 👈

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

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

- **New Features**
- Introduced the ability to convert rich text documents into Markdown,
supporting a wide range of content types such as headings, lists,
tables, images, code blocks, attachments, and embedded documents.
- Added support for parsing collaborative document structures and
rendering them as structured Markdown or parsed representations.
- Enhanced handling of database and table blocks, including conversion
to Markdown tables with headers and cell content.

- **Documentation**
  - Added a README noting the use of a forked Markdown converter.

- **Tests**
  - Added new test coverage for document parsing features.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->


#### PR Dependency Tree


* **PR #12840** 👈

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

packages/common/reader/__tests__/reader.spec.ts

@@ -5,6 +5,7 @@ import { expect, test } from 'vitest';
 import { applyUpdate, Array as YArray, Doc as YDoc, Map as YMap } from 'yjs';
 
 import {
+  parsePageDoc,
   readAllBlocksFromDoc,
   readAllDocIdsFromRootDoc,
   readAllDocsFromRootDoc,
@@ -100,3 +101,20 @@ test('should read all doc ids from root doc snapshot work', async () => {
   const docIds = readAllDocIdsFromRootDoc(rootDoc);
   expect(docIds).toMatchSnapshot();
 });
+
+test('should parse page doc work', () => {
+  const doc = new YDoc({
+    guid: 'test-doc',
+  });
+  applyUpdate(doc, docSnapshot);
+
+  const result = parsePageDoc({
+    workspaceId: 'test-space',
+    doc,
+    buildBlobUrl: id => `blob://${id}`,
+    buildDocUrl: id => `doc://${id}`,
+    renderDocTitle: id => `Doc Title ${id}`,
+  });
+
+  expect(result).toMatchSnapshot();
+});