Original code by @p0llux12 - Discord
- Introduced `SurfsharkVPN` class for proxy service integration.
- Updated configuration to include `surfsharkvpn` in proxy providers.
- Removed legacy `nordvpn` configuration from YAML.
- Enhanced `dl.py` and `search.py` to utilize `SurfsharkVPN`.
* Introduced `SubtitleCodecChoice` to allow selection of subtitle codecs with support for enum names, values, and common aliases.
* Updated `--sub-format` option in `dl.py` to utilize the new `SubtitleCodecChoice`.