This module needs way reworked to just be a state machine. I was trying
to get way too tricky with it so I went back to the drawing board and
made a state machine diagram for it. The diagram is included with this
commit. I also moved the current collection of documentation to a doc/
folder, and added a second-long audio rom to test everything out once
the rom_sd is working.
I moved around where packages are. I couldn't find any evidence of where
other people put them, but for now they are in the `lib/` folder. Other
infrastructure changes are that all the weird includes we need to make
the linter happy are gated behind ifdefs, so they don't mess with
vivado.
I kinda can't believe concurrent assertions work because there's so
little info about them, good to ssee they actually do something
