## Overview
- make lint / make format
- added a PR labeler
## Type of change
**Type:** Infra
## Related issues/PRs
<!-- Link to related issues, feature PRs, or discussions (if applicable)
-->
- GitHub issue:
- Feature PR:
<!-- For LangChain employees, if applicable: -->
- Linear issue:
- Slack thread:
## Checklist
<!-- Put an 'x' in all boxes that apply -->
- [x] I have read the [contributing guidelines](README.md)
- [x] I have tested my changes locally using `docs dev`
- [x] All code examples have been tested and work correctly
- [x] I have used **root relative** paths for internal links
- [x] I have updated navigation in `src/docs.json` if needed
- [x] I have gotten approval from the relevant reviewers
- [ ] (Internal team members only / optional) I have created a preview
deployment using the [Create Preview Branch
workflow](https://github.com/langchain-ai/docs/actions/workflows/create-preview-branch.yml)
## Additional notes
<!-- Any other information that would be helpful for reviewers -->
* Update lexer
* Update parser to use lexer
* Add unit tests for lots of basic cases
* Best effort at preserving HTML blocks
* Preserve indentation in code blocks
* Fix some issues in existing parser
* Add placeholder lexer
The implementations may be replaced with the python `markdown` and
`https://facelessuser.github.io/pymdown-extensions/` -- investigating
whether all extensions are supported.
Lauren Hirata Singh