Bring folk-live-build into this repo

[osnr]

The whole repo https://github.com/FolkComputer/folk-live-build has been put into the live-build subdirectory of this repo (preserving history, although old revisions may not build out of the box since repo/submodule/symlink paths are messed up). I've wanted to do this so we can version package dependencies / OS setup dependencies alongside the corresponding Folk code.

Fixes https://github.com/FolkComputer/folk-live-build/issues/6.

README has been updated to point to the Releases page on this repo instead of on folk-live-build, and I've made a new release with an updated live img.

Not strictly necessary to review since it doesn't touch Folk core, but feel free -- will probably merge tomorrow.

Follow-up tasks:

• make a new release based on main branch (so people can pull and it'll work)
• vendor apriltag repo (this would clean things up further, we have some weird special cases and symlinks for it still)
• outstanding folk-live-build bugs: nvidia drivers, ssh key persistence
• make permanent installer work

[osnr]

(Merging now, and deleting the folk-live-build repo.)