Config UI improvements

[Stvad]

A follow up to #66.

Now that UI for config exists it'd be nice if:

• [ ] For snapshot directory we can select it via QFileDialog

• [ ] For 'root decks' we can select them from the list of existing decks (can maybe reuse some widget from main Anki for this one?)

• [ ] For 'sort methods' we can select the ones we want from the provided list of things. (Ordering here makes things a bit more complicated)

• [ ] Also on mac the section headers proportions are weird:

[ohare93]

These improvements would indeed be good to get done! :+1:

It is still strange that your UI is so overly massive compared to mine :thinking: Do you always full screen everything, perhaps? :sweat_smile:

[Stvad]

I think it's different os + different screen dpi