Use version-controlled SwellStaticFiles

[mranst]

Description

I set up a local repository for SwellStaticFiles using git-annex. This works by storing files in an annex location and having git only manage symlinks to those files, updating the links whenever changes are made. This makes for a more lightweight process. We can keep this as a local repository for now, but we can eventually add remotes such as s3 or other backup locations. I propose to pin versions of those files to worktrees in the static files location (for example, I called the preliminary versions v0.0.0). We can make changes in the develop version, then create a tag and new worktree when we want to switch versions. These files are identical to the ones Swell has been using up until now so there's zero diff, I did add a basic readme briefly explaining git-annex in the repository.

[mathomp4]

I'm going to mention @tclune here. Only because this is a good reminder to look at git-annex. @mranst says it's working for him, so maybe some of the weird NFS issues we had in the past are now better?