Keyboard: Add handwired/pteron config and keymaps (#4060)

* Added pteron files made via from kbfirmware.com.

* Added readme.

* Made some progress on Pteron keymap.

* More keymap.

* Updated bootloader, added some keymap illustrations.

* Moved default keymap to FSund, made default keymap from default preonic keymap.

* Fixed typo in default pteron keymap.

* Made changes recommended by drashna.

keyboards/handwired/pteron/config.h

@@ -0,0 +1,34 @@
+#pragma once
+
+#include "config_common.h"
+
+/* USB Device descriptor parameter */
+#define VENDOR_ID       0xFEED
+#define PRODUCT_ID      0x6060
+#define DEVICE_VER      0x0001
+#define MANUFACTURER    QMK Community
+#define PRODUCT         Pteron Keyboard
+#define DESCRIPTION     Pteron Keyboard
+
+/* key matrix size */
+#define MATRIX_ROWS 5
+#define MATRIX_COLS 12
+
+/* key matrix pins */
+#define MATRIX_ROW_PINS { D7, E6, B4, B5, B6 }
+#define MATRIX_COL_PINS { F4, F6, F5, F7, B1, B3, C6, D4, D0, D1, D2, D3 }
+#define UNUSED_PINS
+
+/* COL2ROW or ROW2COL */
+#define DIODE_DIRECTION ROW2COL
+
+/* Set 0 if debouncing isn't needed */
+#define DEBOUNCING_DELAY 5  // 5 is default
+
+/* 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