Fix GitHub Actions workflow

[striezel]

Currently, the CI workflow to deploy the gh-pages fails. See e. g. https://github.com/ferrilab/bitvec/actions/runs/3500371119/jobs/5862965920 for an example. It fails with the error message:

mdbook: /lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.29' not found (required by mdbook)
mdbook: /lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.28' not found (required by mdbook)
Error: Process completed with exit code 1.

The current version of the action peaceiris/actions-mdbook only supports Ubuntu 22.04 or 20.04, but not Ubuntu 18.04 anymore. So an update of the runner from Ubuntu 18.04 to Ubuntu 22.04 is probably the best way to fix this.

Furthermore, the action actions/checkout is updated to get rid of a deprecation warning related to an old Node.js version.

[myrrlyn]

Hi! I apologize for the long delay; I have had a very stressful winter and have not had the time or energy to check this repository in a timely manner. I'm trying to catch up now.

I don't know anything about GHA and rely entirely on copy-paste or the goodwill of others.

Thank you for catching this.

[striezel]

I apologize for the long delay; I have had a very stressful winter and have not had the time or energy to check this repository in a timely manner. I'm trying to catch up now.

Glad to see you are back. 👍
The PR finally got merged and the CI jobs seem to be passing again, so I see this as a positive outcome, despite the delay.

I don't know anything about GHA and rely entirely on copy-paste or the goodwill of others.

Actually, you can get away with copy and paste for the simpler things of GHA most of the time. :)