Update GitHub Actions tags to digests

[lukehinds]

Digests are considered more secure, as it fixes the action to a specific commit

Check out GitHubs documentation
for more information on why this is important.

You already have dependabot enabled, all future updates will be pinned to digests 🚀

I generated this change using Frizbee,
an open source tool that flips tags to digests in Dockerfiles and GitHub Actions.

I created a second PR that add's the Frizbee action to the repository,
which will flip any future tags to digests automatically.