lfrc - Added hotkey which compresses selected videos (webm,mkv,mp4) via ffmpeg

[TheYellowArchitect]

It is essentially a glorified ffmpeg -i input.video -vcodec libx265 -crf "$compressionRatio" output.mp4

1. It checks if a non-video file is selected (skips it)
2. It properly parses .mp4 to .mp4 (by temporarily renaming the original file)
3. Automatically deletes the original file, but only if it finished conversion (so you can safely interrupt this operation)
4. Notifies the user on completion (so you can mass-compress some olde folder and Super+Shift+9 and continue your work)

Mapped into a hotkey (Alt+x) because it fits near the extract. But change freely. Keep in mind it must not conflict the keymaps added in https://github.com/LukeSmithxyz/voidrice/pull/1374 and https://github.com/LukeSmithxyz/voidrice/pull/1373