Trim video/audio duration so that part can only be downloaded

[TechnologyFuturesInstitute]

Add a timestamp feature that enables a video or audio to be trimmed.

There is no current alternative which offers this service for free.

For example:
If I found a clip in a 1-hour video and I want to download a specific 5-minute clip in it, I should be able to input its timestamp and download what's only in that timestamp provided. Same applies to audio files.

[ihatespawn]

duplicate of #375, #442, #528, https://discord.com/channels/1049706293700591677/1252174896612773988, https://discord.com/channels/1049706293700591677/1243953661118255146, it was being worked on in #350 and i'm 99% sure it's being worked on in the svelte rewrite (https://github.com/imputnet/cobalt/tree/svelte)