Prevent clang-format messing up placeholder tokens within keyboard templates (#6790)

* Use .template file extension for keyboard template files

* Filter out .template files completely before passing to clang-format

* Undo file extension stuff; just ignore quantum/template dir

quantum/template/base/keyboard.h

@@ -0,0 +1,35 @@
+/* Copyright %YEAR% %YOUR_NAME%
+ *
+ * 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 "quantum.h"
+
+/* This a shortcut to help you visually see your layout.
+ *
+ * The first section contains all of the arguments representing the physical
+ * layout of the board and position of the keys.
+ *
+ * The second converts the arguments into a two-dimensional array which
+ * represents the switch matrix.
+ */
+#define LAYOUT( \
+    k00, k01, k02, \
+      k10,  k11   \
+) \
+{ \
+    { k00, k01,   k02 }, \
+    { k10, KC_NO, k11 }, \
+}