Add `Audio Only` & `Worst` options to task queue preferred quality

[ScrubN]

          Please add "Audio Only" option to the task queue.

Originally posted by @ZeusLT in https://github.com/lay295/TwitchDownloader/issues/955#issuecomment-1983985427

Prerequisites:

• [x] Do not hard code enqueuer file extension
• [x] Figure out keywords for the clip downloader (preferred), or hide certain options when enqueuing clips

[ScrubN]

In order to achieve this, we should probably move the current file extension guessing from CLI to Core so we aren't hard coding in the enqueuer: https://github.com/lay295/TwitchDownloader/blob/1afcc3ce2166ab128cb6ca0463fae46acc2e59b5/TwitchDownloaderCLI/Modes/DownloadVideo.cs#L50-L58 https://github.com/lay295/TwitchDownloader/blob/1afcc3ce2166ab128cb6ca0463fae46acc2e59b5/TwitchDownloaderWPF/WindowQueueOptions.xaml.cs#L477-L480

[superbonaci]

I think the whole file extension guessing is something done only on Windows, and generally speaking it shouldn't matter. quality should be the only way to set what has to be downloaded, any file extension or none at all.

[ScrubN]

FFmpeg uses the file extension to automatically determine several things.

[ScrubN]

After #998, we may as well add the "worst" keyword to the enqueuer as well.