Add documents site (#1767)

* feat: add docs site

- Implemented dynamic routing for MDX documentation pages with language support.
- Created layout components for documentation with a header and footer.
- Added metadata for various documentation sections in English and Chinese.
- Developed initial content for the DeerFlow App and Harness documentation.
- Introduced i18n hooks and translations for English and Chinese languages.
- Enhanced header component to include navigation links for documentation and blog.
- Established a structure for tutorials and reference materials.
- Created a new translations file to manage locale-specific strings.

* feat: enhance documentation structure and content for application and harness sections

* feat: update .gitignore to include .playwright-mcp and remove obsolete Playwright YAML file

* fix(docs): correct punctuation and formatting in documentation files

* feat(docs): remove outdated index.mdx file from documentation

* fix(docs): update documentation links and improve Chinese description in index.mdx

* fix(docs): update title in Chinese for meta information in _meta.ts

.gitignore

@@ -54,3 +54,4 @@ web/
 # Deployment artifacts
 backend/Dockerfile.langgraph
 config.yaml.bak
+.playwright-mcp