Added Contra keyboard support (#2501)

* Added Contra keyboard support

The configuration came from a source distribution of the firmware on the
Contra's official website.

I have also included a simple MIDI keymap. (And it works!)

* Changes to Contra config and README

* Readme has been changed as requested by jackhumbert
* Config has been changed to add the Cartel and Contra names to
  the USB configuration.

keyboards/contra/config.h

@@ -0,0 +1,58 @@
+#ifndef CONFIG_H
+#define CONFIG_H
+
+#include "config_common.h"
+
+/* USB Device descriptor parameter */
+#define VENDOR_ID       0xFEED
+#define PRODUCT_ID      0x6060
+#define DEVICE_VER      0x0001
+#define MANUFACTURER    Cartel
+#define PRODUCT         Contra
+#define DESCRIPTION     Keyboard
+
+/* key matrix size */
+#define MATRIX_ROWS 4
+#define MATRIX_COLS 12
+
+/* key matrix pins */
+#define MATRIX_ROW_PINS { F6, B3, B2, B6 }
+#define MATRIX_COL_PINS { F4, F5, B5, B4, E6, D7, C6, D4, D0, D1, D2, D3 }
+#define UNUSED_PINS
+
+/* COL2ROW or ROW2COL */
+#define DIODE_DIRECTION COL2ROW
+
+/* number of backlight levels */
+
+#ifdef BACKLIGHT_PIN
+#define BACKLIGHT_LEVELS 0
+#endif
+
+/* Set 0 if debouncing isn't needed */
+#define DEBOUNCING_DELAY 5
+
+/* Mechanical locking support. Use KC_LCAP, KC_LNUM or KC_LSCR instead in keymap */
+#define LOCKING_SUPPORT_ENABLE
+
+/* Locking resynchronize hack */
+#define LOCKING_RESYNC_ENABLE
+
+/* key combination for command */
+#define IS_COMMAND() ( \
+    keyboard_report->mods == (MOD_BIT(KC_LSHIFT) | MOD_BIT(KC_RSHIFT)) \
+)
+
+/* prevent stuck modifiers */
+#define PREVENT_STUCK_MODIFIERS
+
+
+#ifdef RGB_DI_PIN
+#define RGBLIGHT_ANIMATIONS
+#define RGBLED_NUM 0
+#define RGBLIGHT_HUE_STEP 8
+#define RGBLIGHT_SAT_STEP 8
+#define RGBLIGHT_VAL_STEP 8
+#endif
+
+#endif