[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/64key/config.h

@@ -0,0 +1,34 @@
+/* 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"
+
+#define MATRIX_ROWS 8
+#define MATRIX_COLS 8
+
+#define MATRIX_ROW_PINS { D1, D0, D4, C6, D7, E6, B4, B5 }
+#define MATRIX_COL_PINS { F4, F5, F6, F7, B1, B3, B2, B6 }
+#define UNUSED_PINS { D3, D2 }
+
+/* LEDs are not used in the standard 64key configuration. */
+#define RGB_DI_PIN D3
+#define RGBLED_NUM 0
+
+#define DIODE_DIRECTION COL2ROW
+
+#define PERMISSIVE_HOLD