expose tosc_vwrite

[s-ol]

this can be useful for wrapping the writing method; e.g. like this:

void send(const char *addr, const char *fmt, ...) {
  static uint8_t tx_buf[256];

  va_list args;
  va_start(args, fmt);

  size_t len = tosc_vwrite(
    tx_buf, sizeof(tx_buf),
    addr, fmt, args
  );

  va_end(args);

  slip_send(tx_buf, len);
}

[s-ol]

great library btw - i tried embedding a couple others on Arduino and they were either too bloated or flat out didn't work (not not compile, but crash etc). This one is lean and perfect!