rename api docs to internals

docs/_summary.md

@@ -88,11 +88,11 @@
 * Other Topics
   * [Using Eclipse with QMK](eclipse.md)
 
-* QMK API (In Progress)
-  * [Defines](api_defines.md)
-  * [Input Callback Reg](api_input_callback_reg.md)
-  * [Midi Device](api_midi_device.md)
-  * [Midi Device Setup Process](api_midi_device_setup_process.md)
-  * [Midi Util](api_midi_util.md)
-  * [Send Functions](api_send_functions.md)
-  * [Sysex Tools](api_sysex_tools.md)
+* QMK Internals (In Progress)
+  * [Defines](internals_defines.md)
+  * [Input Callback Reg](internals_input_callback_reg.md)
+  * [Midi Device](internals_midi_device.md)
+  * [Midi Device Setup Process](internals_midi_device_setup_process.md)
+  * [Midi Util](internals_midi_util.md)
+  * [Send Functions](internals_send_functions.md)
+  * [Sysex Tools](internals_sysex_tools.md)