Rename tutte_coxeter_36e -> tutte_coxeter_36k

It was e for edge, now k for keys. Why? I'm toying with ideas
for a full Tutte Coxeter graph (30 vertices/nodes/GPIO pins,
45 edges/switches) incuding 42 keys plus a rotary encoder
(these act like three switches: clockwise, anticlockwise,
press - so 42 edges for normal keys + 3 edges for a rotary
encoder gives 42 + 3 = 45 edges) which could be named with
suffix 43ke.

keyboards/tutte_coxeter_36k/keymaps/default/keymap.c

@@ -0,0 +1,27 @@
+// Copyright 2023 QMK
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include QMK_KEYBOARD_H
+
+const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
+     /*
+      * ┌───┬───┬───┬───┬───┐       ┌───┬───┬───┬───┬───┐
+      * │ Q │ W │ E │ R │ T │       │ Y │ U │ I │ O │ P │
+      * ├───┼───┼───┼───┼───┤       ├───┼───┼───┼───┼───┤
+      * │ A │ S │ D │ F │ G │       │ H │ J │ K │ L │ ; │
+      * ├───┼───┼───┼───┼───┤       ├───┼───┼───┼───┼───┤
+      * │ Z │ X │ C │ V │ B │       │ N │ M │ , │ . │ / │
+      * └───┴───┴───┴───┴───┘       └───┴───┴───┴───┴───┘
+      *           ┌───┐                   ┌───┐
+      *           │GUI├───┐           ┌───┤Alt│
+      *           └───┤Bsp├───┐   ┌───┤Ent├───┘
+      *               └───┤   │   │   ├───┘
+      *                   └───┘   └───┘
+      */
+    [0] = LAYOUT_split_3x5_3(
+        KC_Q,    KC_W,    KC_E,    KC_R,    KC_T,                               KC_Y,    KC_U,    KC_I,    KC_O,    KC_P,
+        KC_A,    KC_S,    KC_D,    KC_F,    KC_G,                               KC_H,    KC_J,    KC_K,    KC_L,    KC_SCLN,
+        KC_Z,    KC_X,    KC_C,    KC_V,    KC_B,                               KC_N,    KC_M,    KC_COMM, KC_DOT,  KC_SLSH,
+                                   KC_LGUI, KC_BSPC, KC_SPC,           KC_SPC,  KC_ENT,  KC_RALT
+    )
+};