GitHub Actions workflows

Would you be interested in having GA workflows being added to the repository? I could provide you these workflows:

• CI workflow triggered on PRs:
  • Does formatting checking
  • Runs clippy
  • Runs tests
• CD workflow triggered when pushing a git tag:
  • Pushes a new version to crates.io

Additionally, the following could be done:

• CI workflow for scheduled spinner updates:
  • Runs a cron job to update the spinners automatically. If updates do take place, a new patch version is published.

An alternative to the last workflow would be to turn the update_spinners script into a build script. That way, the files are always up-to-date. Compilation would be longer though (maybe 2sec-5sec, depending on the internet connection).