pass arguments to yt-dlp in SimpleYoutubeDLGui.py

**Is your feature request related to a problem? Please describe.**
In order to be able to freely control yt-dlp behaviour, especially the [download](https://github.com/yt-dlp/yt-dlp#workarounds) and [geo-unblocking](https://github.com/yt-dlp/yt-dlp#geo-restriction) options, a input field for command line arguments passed to yt-dlp shall be provided.

**Describe the solution you'd like**
I'd like to set the argument ``--add-header "Referer:"`` to download a specific video via yt-dlp that is hosted on a cdn that checks the Referer HTTP Header to be a specific url.