[Keymap] snowkuma Planck keymap (#6225)

* Snowkuma's planck layout.

Heavily influenced by both Planck and SDOTHUMs layouts.  I have tried to
implement a comfortable layout with a wide stagger and a minimal set of
key usage.

Still a work in progress, hope it is useful to others.

* Adds simple readme file and images of layout

* Removes unused experimental definitions

* Update readme.md

Adds images of layout to readme.

* Removes accidentally added test keymap .swn .swo .swp files

* Updates config.h replaces include guard

As suggested by @noroadsleft replaces the include guard (ifndef, define
and endif) with just `#pragma once`.

* Replaces two extra KC with inbuilt QMK equivalents

custom_keycodes.h
Replaces `___f___` with the equivalent QMK alias `_______` KC_TRNS
`___x___` with the equivalent QMK alias `XXXXXXX` KC_NO

Updates keymap.c to reflect the changes made.

* Changes keymap.c to include QMK_KEYBOARD_H

Replaces planck.h and action_layer.h includes with the single inclusion
of QMK_KEYBOARD_H which includes action_layer.h automatically.

* Update keyboards/planck/keymaps/snowkuma/keymap.c

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

* Update keymap.c

removes unused Coleman key code from enum planck_keycodes

* Update keymap.c removes COLEMAK key code logic

keyboards/planck/keymaps/snowkuma/config.h

@@ -0,0 +1,46 @@
+#pragma once
+
+#ifdef AUDIO_ENABLE
+    #define STARTUP_SONG SONG(PLANCK_SOUND)
+    // #define STARTUP_SONG SONG(NO_SOUND)
+
+    #define DEFAULT_LAYER_SONGS { SONG(QWERTY_SOUND), \
+                                  SONG(COLEMAK_SOUND), \
+                                  SONG(DVORAK_SOUND) \
+                                }
+#endif
+
+/*
+ * 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
+
+// Settings for homerow mods
+#define TAPPING_TERM 250
+#define IGNORE_MOD_TAP_INTERRUPT
+
+
+// Add the leader key feature
+#define LEADER_TIMEOUT 300