Docs

File descriptions:

links.txt contains useful links i would like to keep
6809-sn74ls612_timing.md contains notes on the mmu and cpu interface
tech-spec.md contains basic info on layout of system (outdated)
timing.html contains info on vga timing pulled from https://martin.hinner.info/vga/timing.html
vga_ram.txt contains notes on ram size for the vga card
video_timing.txt contains output from the python script linked in the first entry of links.txt. it has some timing settings for the upd72020 for different resolutions