Docusaurus upgrade 2 -> 3

[patdavid]

This issue is to track progress on the upgrade from Docusaurus 2 -> 3.

I've done a preliminary manual upgrade for packages in package.json.

The Prism theme has a new method for calling it that I had to fix in docusaurus.config.js.

The site builds, but when serving it locally via yarn start there is still an overlay error for webpack. I'm investigating if it's a show stopper or only a dev thing.

[patdavid]

I'm working in this branch:

https://github.com/Ondsel-Development/website/tree/pat/docusaurus_v3

I also updated some old blog posts to make the MDX work properly with v3.