This patch implements documentation linter, which leaves under `test/doclint`
folder.
The documentation linter works like this:
1. Parse javascript source code with esprima and construct a "documentation" out of source code
2. Generate HTML out of `api.md` and traverse the HTML with puppeteer.
3. Make sure javascript aligns nicely with HTML
The documentation linter adds the following commands:
- `yarn doc` - to test that documentation covers all the relevant apis
- `yarn generate-toc` - to update the table-of-contents for the `api.md`
