[Keyboard] Set reasonable defaults for Corne keyboard (#13440)

* [Keyboard] Set reasonable defaults for Corne keyboard

* Add note about bootmagic

* Make bootmagic config super weak

* cleanup

* Apply suggestions from code review

* Update keyboards/crkbd/readme.md

keyboards/crkbd/post_config.h

@@ -0,0 +1,31 @@
+/* Copyright 2020 Christopher Courtney, aka Drashna Jael're  (@drashna) <drashna@live.com>
+ *
+ * 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
+
+#ifndef BOOTMAGIC_LITE_ROW
+#    define BOOTMAGIC_LITE_ROW 0
+#endif
+#ifndef BOOTMAGIC_LITE_COLUMN
+#    define BOOTMAGIC_LITE_COLUMN 1
+#endif
+
+#ifndef BOOTMAGIC_LITE_ROW_RIGHT
+#    define BOOTMAGIC_LITE_ROW_RIGHT 4
+#endif
+#ifndef BOOTMAGIC_LITE_COLUMN_RIGHT
+#    define BOOTMAGIC_LITE_COLUMN_RIGHT 1
+#endif