feat: add basic rotation for 270 degrees

[danjenkins]

More angles to be added once we agree on this concept being ok.

This is essentially what I've had to do to be able to create a vertical output using 128x64 display.

I've just moved the logic to the lib.

Its not ideal, but the hub75 driver doesn't support rotation so you have to do it on the buffer level. I think we'd want to only support 0/90/180/270 which is still better than nothing.

Let me know what you think.

[andrewjw]

This looks great. I'm keen to have rotation supported because although I only have a 64x64, it'd be easier if the power cable was in a different location.

I agree that we only want to support 0, 90, 180 or 270. Anything else just wouldn't work. Can you add an assertion to force it only accept those values?

I've been thinking about how to balance speed and readability. I was thinking of having a set of functions like _rotate_0, _rotate_90 etc, and then in constructor just assigning the correct one to a member variable. You can then call that in the pixel setting functions. You get the downside of a function call even in the 0 degrees case, but avoid comparing to the rotation each time. Hope that makes sense, and happy to accept something else if you think it make sense when adding the rest of the angles.

The last thing is that we should add some tests to verify that pixels get rotated correctly.

[danjenkins]

Great I'll tackle this soon and get tests/assertions in etc