[Keymap] Romain's Preonic layout (#7067)

* Add customized preonic layout

* Add a README detailing a bit the differences from the default preonic layout

* Apply suggestions from code review

Co-Authored-By: fauxpark <fauxpark@gmail.com>

* Remove unnecessary end-of-line backslashes

* Import fix for startup sound (thanks @drashna)

* Remove unnecessary layers and keycodes

* Bring back the _QWERTY layer code

Co-Authored-By: noroadsleft <18669334+noroadsleft@users.noreply.github.com>

keyboards/preonic/keymaps/cranium/config.h

@@ -0,0 +1,38 @@
+#pragma once
+
+
+#ifdef AUDIO_ENABLE
+    #define STARTUP_SONG SONG(PREONIC_SOUND)
+    // #define STARTUP_SONG SONG(NO_SOUND)
+
+    #define DEFAULT_LAYER_SONGS { SONG(QWERTY_SOUND), \
+                                  SONG(COLEMAK_SOUND), \
+                                  SONG(DVORAK_SOUND) \
+                                }
+#endif
+
+#define MUSIC_MASK (keycode != KC_NO)
+
+/*
+ * MIDI options
+ */
+
+/* Prevent use of disabled MIDI features in the keymap */
+//#define MIDI_ENABLE_STRICT 1
+
+/* enable basic MIDI features:
+   - MIDI notes can be sent when in Music mode is on
+*/
+
+#define MIDI_BASIC
+
+/* enable advanced MIDI features:
+   - MIDI notes can be added to the keymap
+   - Octave shift and transpose
+   - Virtual sustain, portamento, and modulation wheel
+   - etc.
+*/
+//#define MIDI_ADVANCED
+
+/* override number of MIDI tone keycodes (each octave adds 12 keycodes and allocates 12 bytes) */
+//#define MIDI_TONE_KEYCODE_OCTAVES 2