[DOC]: Instructions for hosting docs locally don't work

### Is this a duplicate?

- [X] I confirmed there appear to be no [duplicate issues](https://github.com/NVIDIA/cccl/issues) for this bug and that I agree to the [Code of Conduct](CODE_OF_CONDUCT.md)

### Is this for new documentation, or an update to existing docs?

New

### Describe the incorrect/future/missing documentation

The following instructions from `cccl/libcudacxx/docs/readme.md` don't work flawlessly:

> To build and serve the documentation as a website to `http://localhost:4000` just execute the following from libcudacxx root directory:

```shell
./docs/serve
```

It seems that the currently configured `base_url` [(link](https://github.com/NVIDIA/cccl/blob/54fd4c00a8a796d4d4497ccd82651768539d5e30/libcudacxx/docs/_config.yml#L16)) does not work when hosting locally with a port.

The following change solves the problem locally, but not sure if that affects the hosted docs:
```
baseurl: "/cccl/libcudacxx"
```

### If this is a correction, please provide a link to the incorrect documentation. If this is a new documentation request, please link to where you have looked.

https://github.com/NVIDIA/cccl/tree/main/libcudacxx/docs