Documentation for release

sub-tasks will be created as needed but here's a list of things we need to document
- local build process (for those who prefer homegrown compute)
- switching from t2-ostree to t2-bootc (image parity, etc)
- updates / rollback (for DEs as well as 
- filesystem limitations / mutability
- additional software (without layering, using systemd-sysext or whatever)
- support channels