[Keyboard] Add Xiaomi MK02 (#7825)

* [Keyboard] Added xiaomi/mk02

* keyboards/xiaomi/mk02: cleanup

* keyboards/xiaomi/mk02: add linker script

* update readme

* update

* remove via (crashes during startup)

* LAYOUT => LAYOUT_tkl_ansi

* Change vid/pid

* Add a warning to the readme

keyboards/xiaomi/mk02/mk02.c

@@ -0,0 +1,8 @@
+#include "mk02.h"
+
+void bootloader_jump(void) {
+    uint32_t *magic_address = (void*)0x20000FFC;
+    *magic_address = 0x626c6472;
+
+    NVIC_SystemReset();
+}