[Keyboard] Add Karn Keyboard (#19846)

Co-authored-by: jack <0x6a73@protonmail.com>
Co-authored-by: Joel Challis <git@zvecr.com>
Co-authored-by: Drashna Jaelre <drashna@live.com>

keyboards/karn/keymaps/colemak/config.h

@@ -0,0 +1,13 @@
+// Copyright 2023 Robert Mills (@robcmills)
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+// Equivalent to zmk behavior-hold-tap tap-preferred flavor
+// Do not force the mod-tap key press to be handled as a modifier
+// if any other key was pressed while the mod-tap key is held down.
+#define IGNORE_MOD_TAP_INTERRUPT_PER_KEY
+
+// Equivalent to zmk behavior-hold-tap hold-preferred flavor
+#define HOLD_ON_OTHER_KEY_PRESS_PER_KEY
+