Add condition to keep video paused if leader leaves/changes

[mattman107]

Hello let me preface this PR with this is my first time using Haxe, and I am by no means a web developer. So please look this over and let me know if I messed anything up or if there is anything problematic with my logic here.

What brought my desire for this feature to be a thing is that my friends and I sometimes pause videos and leave them in the queue for a couple of days. I realized that if all users disconnected from the webpage, and one person rejoined the video would unpause. This kind of sucked because we would then have to re-add the video to the queue or the person who rejoined would have to manually pause it.

I have added a new boolean variable in the default-config.json and referenced it in the server Main.hx file to control when a video should resume. I set it to false by default so videos won't resume in these scenarios (of course if you would prefer it be true we can go with that).