git: collapse autogenerated HTML docs in GitLab

GitLab 16.10 introduced a feature to automatically collapse autogenerated files (e. g. lock files) in merge requests. The benefit is a more clean merge request experience, as well reducing load on the GitLab instance.

This is also useful to enable for other kinds of autogenerated files.

In usp-js, the public directory is autogenerated, and is quite noisy when viewing commits/merge requests.

Autocollapse all files in the public directory.