[Keyboard] Concertina (#11922)

* [Keyboard] Concertina

* Added a novel handwired keyboard.

* Concertina lint

* Perfunctory changes to pass CI.

* Concertina line width

* Changes from code review: GPL headers, modernization, full-width
  representation of matrix to match info.json.

keyboards/handwired/concertina/config.h

@@ -0,0 +1,26 @@
+/* Copyright 2020-2021 Viktor Eikman
+ *
+ * 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/>.
+ */
+
+#pragma once
+
+#include "config_common.h"
+
+/* USB device descriptors */
+#define VENDOR_ID       0x444D
+#define PRODUCT_ID      0x3632
+#define DEVICE_VER      0x0001
+#define PRODUCT         Concertina
+#define MANUFACTURER    Viktor Eikman