[FR]: Option to always add feeds in advanced mode

[RetroAbstract]

Brief description of the feature request

This feature would allow the user to always add feeds in advanced mode.

I add feeds fairly regularly and I never use the "Discover feeds" feature, it would be nice to be able to set RSS Guard to skip the feature and always open the advanced mode when adding new feeds, just like it was before the "Discover feeds" feature was introduced.

The option could be added in Settings > General > Always add new feeds in advanced mode.

Thanks!