Xton's first keymap! (#2941)

* FORK!

* WIP - just how i like it

* empty

* more movement

* mouse keys

* more vimminess

* append/insert shift

* WIP - vim macros

* blocked out layer below in cmd mode.

also, about to restart my cmd approach.

* WIP - new vim layer

ripoff of the ergodox one, but rewritten as a state machine.

* debugged some, got key repeat working

* moooar coverage

* moooar coverage

* regular vis mode

* basically done with basics.

* some refactoring

- common movement sequences into helper function
- added some rgb controls

* modkey passthru feature

* stdized on cmd-left/right instead of ctrl-a/e

sadly. as there's no reliable shift-ctrl-e

* indicator lights

* moved vim layer into userspace

* cleaned up some yanking edge cases

* docs and some tweaks to layerescapes

* updated/added license strings

* updated comments

* moved config changes to keymap

* spurious changes removed

keyboards/niu_mini/keymaps/xtonhasvim/readme.md

@@ -0,0 +1,9 @@
+# Xton has a tiny keyboard! With Vim!
+
+Based on the standard Planck layout with a few changes:
+
+* Escape moved to dual-function with control.
+* Dedicated movement and mouse layers.
+* Top and middle row swapped in `_RAISE` and `_LOWER` because I never use F-keys.
+* Vim layers! See `users/xtonhasvim`.
+