break up keymaps and quantum keycodes into files by feature

docs/feature_bluetooth.md

@@ -0,0 +1,13 @@
+# Bluetooth
+
+<!-- FIXME: Document bluetooth support. -->
+
+## Bluetooth Keycodes
+
+This is used when multiple keyboard outputs can be selected. Currently this only allows for switching between USB and Bluetooth on keyboards that support both.
+
+|Name|Description|
+|----|-----------|
+|`OUT_AUTO`|auto mode|
+|`OUT_USB`|usb only|
+|`OUT_BT`|bluetooth|