You can build docs using a modified `doc-gen4` as follows: Replace the `from git "..." @ "main"` in the `lakefile.lean` with just `from "..."` using the path to the modified version of `doc-gen4`. E.g. if the
path to the modified version of `doc-gen4` is `../doc-gen4`, it would be:
```
meta if get_config? env = some "dev" then -- dev is so not everyone has to build it
require «doc-gen4» from "../doc-gen4"
```
The root of the built docs will be `build/docs/index.html`. However, due to the "Same Origin Policy", the
generated website will be partially broken if you just open the generated html files in your browser. You
need to serve them from a proper http server for it to work. An easy way to do that is to run
`python3 -m http.server` from the `build/docs` directory.