Add support for layer labels

[jbarr21]

Thanks a lot for sharing your setup, it is extremely helpful! One thing I noticed is that if you use an OLED widget, it pulls the name of the current layer from the zmk layer label. I know adding this would be a breaking change, so I could see adding this as either:

1. a new param to ZMK_LAYER
2. a copy of ZMK_LAYER w/ the new param but named ZMK_LAYER_LABELED instead like this

If you want this added, I'm happy to put up a PR for whichever fits better with your direction.

[urob]

I am thinking we could just reuse the name parameter which doesn't serve much purpose (or something like oled_ ## name). This way it wouldn't be breaking.

Do you see any reason against this?

[jbarr21]

Using name for symbol works for me

[urob]

I'll try to push the change later tonight.

[urob]

Added as of the latest commit. Let me know if it's not working as intended.

[jbarr21]

works great, thx!