Add "recording" button to Live-Annotator interface
This issue is part of breaking up #1348 (closed) in Todo-issues, where I suggested to add a button that allows you to save the time when you started your video recording, which later allows you to place the video on the Timeline at that time and date.
This is of course not working perfectly, because it's difficult to hit the record button of your camera at exactly the same moment, but if you try as good as possible, the offset won't be too big (and there is some "reaction" offset in live annotation anyway). I've tested this with writing down the time and it works quite well. The "time-save" button is just a little "helper".
Hitting the button creates an annotation with purpose linking (so it shows up in each view of the Timeline). It should say something like "Recording for Live-Annotation session started at hh:mm:ss".
The button does not need the text label like in the screenshot. It can use an "recording" material icon and the tooltip could say something like "saves the current time and date when you hit the button"