Add DirectPinMatrix for diodeless keyboards

[dariogoetz]

I used a ´DirectPinMatrix´ for my firmware for the Cantor. It assumes that each switch is directly attached to an individual pin instead of using a row/column matrix.

I thought, I'd offer the code as it may be of interest for others, too.

[TeXitoi]

Thanks

[camrbuss]

As another option, you can just use the matrix with direct pins in a 1x? configuration.

https://github.com/camrbuss/pinci/blob/main/firmware/src/main.rs

[dariogoetz]

Yes, that would work, too, but I like thinking of the switches as in a matrix. And you don't need to define a "virtual" output pin that is not actually used.