Adding initial version of Sony OA-S3400 converter.

- Not fully reading for usage, but 90% of the way there for typing.
- Some soldering is required for 2 keys to work properly (Shift and Shift Lock)
- Even when complete, be careful when doing multiple key combos, as the key buffer is only cleared when all general keys are released (all except Shift, Shift Lock, and Code)

Keymap/keymap.h

@@ -48,6 +48,7 @@
 #include "kaypro1.h"
 #include "microswitch8304.h"
 #include "sonynews.h"
+#include "sonyoas3400.h"
 #include "tandy1000.h"
 #include "univacf3w9.h"