[Keyboard] Add converter/xmk (#18433)

keyboards/converter/xmk/rules.mk

@@ -0,0 +1,10 @@
+# Copyright 2022 Manna Harbour (@manna-harbour)
+# https://github.com/manna-harbour/xmk
+
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+SRC += xmk_matrix.c
+SRC += xmk_shell.c
+CUSTOM_MATRIX = lite
+
+#XMK_DEBUG = yes