Adding 3 second timeout before autoboot.

ueforth/arduino/autoboot.fs

@@ -11,6 +11,7 @@ internals definitions
 ( Check for autoexec.fs and run if present.
   Failing that, try to revive save image. )
 : autoexec
+   300 for key? if rdrop exit then 10 ms next
    s" /spiffs/autoexec.fs" ['] included catch 2drop drop
    ['] revive catch drop ;
 ' autoexec ( leave on the stack for fini.fs )