GitHub action for building narya in CI

[olynch]

This adds a github action for building a static version of narya in CI. It also uploads the build and its dependencies to a cache, so that local builds of narya/future CI builds of narya can simply pull dependencies from cache.

What it should also do is upload the static narya binary somewhere; that is a TODO.

[mikeshulman]

Until we have a github organization, a natural place to put the binaries would be my github.io site. But if the CI scripts store an access token allowing them to upload to there (or anywhere, really), then that token would be publicly accessible to anyone who clones the repository, which doesn't seem very secure. We do this for the HoTT Book but I didn't set that up, so I don't know how it's secured (or even if it is).

I gather the CI can also create a github "release" which has files attached to it, but that doesn't seem correct for development builds that happen with every commit.

[mikeshulman]

It would also be nice if the CI could update jsNarya somewhere.

[olynch]

Until we have a github organization, a natural place to put the binaries would be my github.io site. But if the CI scripts store an access token allowing them to upload to there (or anywhere, really), then that token would be publicly accessible to anyone who clones the repository, which doesn't seem very secure. We do this for the HoTT Book but I didn't set that up, so I don't know how it's secured (or even if it is).

The CI can have variables which are configured at a repository level, so they won't be in the workflow file and won't be runnable for clones of the repository. So that's not a problem. And I can look into building jsNarya!

[mikeshulman]

Where are the variables configured?

Edit: Oh, I see, we want to use secrets.

[mikeshulman]

Ah, now I remember: github pages can publish from any repository, not just the dedicated one. That doesn't require any secrets or variables or anything.

https://docs.github.com/en/pages/getting-started-with-github-pages/configuring-a-publishing-source-for-your-github-pages-site

So we can either (1) create a special branch such as gh-pages that contains only the static binary and the jsnarya files, and have the CI push to that branch, or (2) use the special github actions such as https://github.com/actions/upload-pages-artifact to create the site directly from the CI.