Update Jekyll and Dependencies

[danyeaw]

We are running older version of most of our dependencies. This was set up since we were using auto deployment with GitHub Actions, but now we have our own build and can run the latest and greatest:

• Ruby 2.7.5, latest is 3.2.2
• Jekyll 3.9.3, latest is 4.3.2
• Bootstrap 4.5.0, latest 5.2.3

We also depend on the github-actions gem which pulls in 40+ dependencies, it would be great to specify only exactly what we need.

[danyeaw]

Since we are using the github-pages gem again, I'm going to go ahead and close this until it upgrades to newer dependencies.