### What problem does this PR solve?
```
RAGFlow(api/default)> parse file 'README.md';
Parsing Markdown file: README.md
--- AST tree:
HTMLBlock '<div align="center">\n<a href="https:…'
```
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
Signed-off-by: Jin Hai <haijin.chn@gmail.com>
