Added a new setting to remember the user's preferred endpoint. When both USB and
BLE are connected, the preferred endpoint will be used.
Added a new behavior to control this setting. It supports commands:
&end END_USB - Prefer USB output
&end END_BLE - Prefer BLE output
&end END_TOG - Toggle between USB and BLE
* Move all headers to `include/zmk` directory.
* Update includes to reference them properly.
* Add `keymap.c` file from keymap, if found.
* Toplevel CONFIG_ZMK_BLE aggregate config setting.
Joel Spadin