Timecode support for adding sounds to soundboard #25

so basically it'd be a good idea to add some parameters to the !board add command specifiying a start and endpoint so we can clip a short segment of video to add to the soundboard e.g:

!board add https://www.youtube.com/watch?v=VOEvlJVjnF0 -start 00:00:23 -end 00:00:27

this should pass the -start and -end params to equivalent ffmpeg parameters to shorten the clip down to the intended segment of audio

Reporter is advised that they are a deer