[Keyboard] Add handwired BDN9-BLE (#8192)

* Add handwired BDN9-BLE

* Apply suggestions from code review

Co-Authored-By: Ryan <fauxpark@gmail.com>

* Update keyboards/handwired/bdn9_ble/rules.mk

Co-Authored-By: Ryan <fauxpark@gmail.com>

* Update keyboards/handwired/bdn9_ble/rules.mk

Co-Authored-By: Ryan <fauxpark@gmail.com>

* Update keyboards/handwired/bdn9_ble/readme.md

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

Co-authored-by: Ryan <fauxpark@gmail.com>
Co-authored-by: James Young <18669334+noroadsleft@users.noreply.github.com>

keyboards/handwired/bdn9_ble/keymaps/default/keymap.c

@@ -0,0 +1,49 @@
+/* Copyright 2019 Danny Nguyen <danny@keeb.io>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include QMK_KEYBOARD_H
+
+
+// Enable test mode, which sets the keys to letters A-I.
+//#define TESTMODE
+
+const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
+    #ifndef TESTMODE
+    // MEH - hold down ctrl, alt, shift, and press key
+    [0] = LAYOUT(
+        MEH(KC_1), MEH(KC_2), MEH(KC_3),
+        MEH(KC_4), MEH(KC_5), MEH(KC_6),
+        MEH(KC_7), MEH(KC_8), LT(1, MEH(KC_9))
+    ),
+    #else
+    [0] = LAYOUT(
+        KC_A, KC_B, KC_C,
+        KC_D, KC_E, KC_F,
+        KC_G, KC_H, KC_I
+    ),
+    #endif
+    /*
+     * ------------------------------------------------------------------------
+     * |                | Automatic BLE output detection | Reset               |
+     * | Backlight Step | Use USB port for output        |                     |
+     * | Backlight Tgl  | Use Bluetooth for output       | (currently pressed) |
+     * ------------------------------------------------------------------------
+     */
+    [1] = LAYOUT(
+        _______, OUT_AUTO, RESET,
+        BL_STEP, OUT_USB, _______,
+        BL_TOGG, OUT_BT,  _______
+    )
+};