Support for a workflow w/ `jj`

[jasikpark]

I'm a big proponent of jj, which offers a useful frontend to git, while designing a new way to think about changes that pulls from Mercurial and Pijul and other VCS's.

• https://jj-vcs.github.io/jj/latest/
• https://steveklabnik.github.io/jujutsu-tutorial/introduction/introduction.html
• https://v5.chriskrycho.com/essays/jj-init/
• https://v5.chriskrycho.com/journal/jujutsu-megamerges-and-jj-absorb/
• https://v5.chriskrycho.com/notes/jj-tip-describe-multiple-revisions-at-once/

Curious to see how this tool interfaces with a jj based workflow. I'm writing this before I've tried out st, but for one I'm excited that it doesn't require 1 pr = 1 commit as SPR and many other tools do.

jj makes rebasing branches quite easy, I'm honestly unsure why it's so much simpler??