Add bank switching and document Testing Workflow

[Rodrigodd]

The only thing missing for passing cpu_instrs.gb was implementing some basic MBC1 bank switching. I also make the timer be more align with the gameroy emulation, so it does not diverge when running 02-interrupts, even if the test was still passing.

I also took a look at mooneye's test roms, but they at least relies on the PPU LY register for functioning, so I will just skip that and go directly to try simulating the entire DMG-CPU soc next, at dmg-sim repo.

I also document my testing workflow, pointing to the tooling I used. I think we can already Close #204.

[ogamespec]

I apologize for the delay, was on the weekend :) Thanks for the work you've done, I'm very interested in what you'll do with running the core on a full-fledged simulator of the whole SoC, I'll keep an eye out :)
I think it's time to do another HDL release :)