Suggested changes to Big Artsey

[carcinization]

Just a collection of some Big Artsey adjustments we've been discussing on the discord server. Here is what I think big artsey base layer should look like (left hand):

Artsey_S, Artsey_T, Artsey_R, Artsey_A, Backspace,
Artsey_O, Artsey_I, Artsey_Y, Artsey_E, Oneshot Shift Key,
Ctrl, @, Delete, Equals, Tab,
MO(1), Space

To access the function layer, I propose that the combo to trigger it should be Backspace and Tab, instead of where it is currently, which would be Backspace and Shift. This is to prevent accidental layer triggers.

I also recommend we consider changing the shift lock combo to be Artsey_R and Delete, instead of R and Y, for the same reason. Obviously this would change parity with normal artsey so should be careful about this, but it might make big artsey easier to use.

Finally I propose we have a full numpad on the number layer, since we have three rows to work with. Not sure yet the best layout but something like that.