[Keyboard] Added Cans12er keyboard (#7455)

* added cans12er keyboard

* updated readme

Updated the readme to conform with the provided template from the qmk_firmware githubpage

* Update keyboards/cans12er/README.md

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

* Changed configuration

Changed the configuration based on the Change Request from PR #7455 made by github user noroadsleft

keyboards/handwired/cans12er/keymaps/default/keymap.c

@@ -0,0 +1,20 @@
+// This is the canonical layout file for the Quantum project. If you want to add another keyboard,
+// this is the style you want to emulate.
+
+#include QMK_KEYBOARD_H
+
+// Each layer gets a name for readability, which is then used in the keymap matrix below.
+// The underscores don't mean anything - you can have a layer called STUFF or any other name.
+// Layer names don't all need to be of the same length, obviously, and you can also skip them
+// entirely and just use numbers.
+
+#define _KEYPAD 0
+
+const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
+
+[_KEYPAD] = LAYOUT_ortho_3x4(
+		KC_A, KC_B, KC_C, KC_D, 
+		KC_E, KC_F, KC_G, KC_H, 
+		KC_I, KC_J, KC_K, KC_L 
+),
+};