Keymap: Add am keymap (#3843)

* Add am keymap

* Add configuration to play nice with stuck modifiers

This is in particular useful with emacs since its easy to get ctrl stuck

* Deactivate mouse keys and backlight

* Add control/esc and shift/enter taps

* Remove DVORAK and PLOVER

I won't be using this soon, so getting some free space

* Raiser and Lower ideas from jeebak

* Add cursor and mouse layers

* Enable mouse keys

* Switch underscore with minus

* Disable audio and fix warnings

* Update to the upstream changes

* VIM line motion symbols on the raise layer

* Enable sound and freeup some media keys on layers

* Fix whitespace on keymap

* Code review changes

* Improve keymap documentation

* Improve keymap to match to the default one

* Restore DEFAULT_FOLDER to the default value

* Fix config.h unescaped line

keyboards/planck/keymaps/am/config.h

@@ -0,0 +1,41 @@
+#pragma once
+
+/* Prevent stuck modifiers */
+#define PREVENT_STUCK_MODIFIERS
+
+#ifdef AUDIO_ENABLE
+    #define STARTUP_SONG SONG(PLANCK_SOUND)
+
+    #define DEFAULT_LAYER_SONGS { SONG(QWERTY_SOUND),   \
+                                  SONG(COLEMAK_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
+
+// Most tactile encoders have detents every 4 stages
+#define ENCODER_RESOLUTION 4