docs(v2.1.0): add comprehensive documentation for flat OPFS structure

- Add F-002 feature spec for flat OPFS structure and in-memory release configs
- Add F-002 document update plan outlining all 17 affected documents
- Add ADR-0008 for auto-migration strategy
- Update S1-S6 documents with v2.1.0 changes (architecture, design, ADRs, implementation)
- Update TODO.md with completed browser compatibility task
- Update package.json (likely version or dependency change)

Author: wuchuheng

TODO.md

@@ -5,4 +5,13 @@
 [x] Docs: add copyright and MIT license in the home page.
 [x] Add github test badge.
 [x] creating some post about how to use sqlite, sql or Relational database. hackernews, devto
-[ ] Browser: List the browser versions that support this library in docs.
+[x] Browser: List the browser versions that support this library in docs.
+
+# 2.0.0
+
+[ ] docs: rename the sidebar title from 'Release' to 'Release (migration)'
+[ ] api: generate a api document for `window.__web_sqlite` to explain the api, and what it does. this document should explain the api in detail,
+help developer tool to understand how to use this library.
+[ ] docs: add sqlite playground in the docs.
+[ ] dev-tools: migration test, this feature should help developer to test the migration process. and try to execute the migration sql in the test evn, then rollback the test evn to the initial state.
+[ ] dev-tools: seed test, the dev tools should create a new dev db, and then execute the seed sql, after the seed sql executed, the dev db should be remove.