Adding binary transfer option for websockets

[j-nik]

In AsyncFsWebServer.h you have the following to allow a websocket broadcast of a text message:

/*
 * Broadcast a websocket message to all clients connected
*/
void wsBroadcast(const char * buffer) {
  m_ws->textAll(buffer);
}

I've added the following below this to allow broadcasts of an array of bytes, which I find quite useful:

/*
 * Broadcast a binary websocket message to all clients connected
*/
void wsBroadcastBinary(uint8_t * message, size_t len) {
  m_ws->binaryAll(message, len);
}

[j-nik]

If you do so augment your library, I've written an example you could consider adding.

https://forum.arduino.cc/t/binary-data-over-websockets-with-the-asyncespfswebserver-library/1258142/3