Add start, stop and resume functionality to mystreamtimer:// input protocol urls

[wseemann]

Hello @jamesmontemagno, great project! I'm currently using this application as a round timer for martial arts bouts streamed via OBS. Since these rounds are often stopped and resumed multiple before the timer expires, is it possible to add urls to start and stop the current counter via mystreamtimer://. I would happily pay to have this functionality added. I would've attempted to add this functionality myself, but I have no idea how to compile this project. Thanks in advance!