Add Keyboard Control Layers

[manna-harbour]

Currently RGB, bluetooth, etc. are on Media but there is not enough space for all keyboard control keycodes. Add a new layer or layers for keyboard control.

• Need to take into account Invoke behaviors with different "locality" zmkfirmware/zmk#547

[manna-harbour]

E.g. BT / output could go on one side and RGB / power on the other, activated with layer-tap on the other hand bottom row middle finger:

* Bluetooth / Output Selection (left)
| &bt BT_CLR    | &bt BT_SEL 7 | &bt BT_SEL 8 | &bt BT_SEL 9 | &out OUT_BLE |
| &bt BT_SEL 11 | &bt BT_SEL 4 | &bt BT_SEL 5 | &bt BT_SEL 6 | &out OUT_TOG |
| &bt BT_SEL 10 | &bt BT_SEL 1 | &bt BT_SEL 2 | &bt BT_SEL 3 | &out OUT_USB |
| U_NP          | U_NP         | &bt BT_PRV   | &bt BT_SEL 0 | &bt BT_NXT   |

* Lighting / External Power / Reset  (right)
| RESET             | &none             | RGB_HUD          | RGB_HUI | &none           |
| RGB_TOG           | RGB_RMOD          | RGB_SAD          | RGB_SAI | RGB_MOD         |
| &bootloader       | &rgb_ug RGB_SPD   | RGB_VAD          | RGB_VAI | &rgb_ug RGB_SPI |
| &ext_power EP_OFF | &ext_power EP_TOG | &ext_power EP_ON | U_NP    | U_NP            |

[manna-harbour]

Keyboard control has been added to Media with the use of shift functions. See https://github.com/manna-harbour/miryoku/tree/master/docs/reference#media.