Update Material for MKDocs dependencies and update image links

[Frichetten]

There have been some recent warnings in our CI/CD pipeline and it would be wise to deal with them.

• Check the status for our Material for MKDocs dependencies and fix as needed
• All images need to be downloaded locally to make sure they don't disappear.

[Frichetten]

Originally this PR was supposed to be fairly easy, but in the time since I created it a new warning has emerged. It looks like MkDocs wan'ts to references images a content and not as a website, so ../../thing.png, instead of /images/thing.png.

This will take a little bit, however it is in the same vein as pulling all images locally, so I suppose this PR should be more about fixing CI/CD warnings.

• [x] Update dependencies
• [x] Pull all images locally
• [x] Update image references to use the right paths.

[Frichetten]

• [x] Need to update the GitHub Action Cache version