After completing the new game wizard but before initializing turn 0,
open a dialog to allow the player to customize their air wing. With this
they can remove squadrons from the game, rename them, add players, or
change allowed mission types. *Adding* squadrons is not currently
supported, nor is changing the squadron's livery (the data in pydcs is
an arbitrary class hierarchy that can't be safely indexed by country).
This only applies to the blue air wing for now.
Future improvements:
* Add squadron button.
* Collapse disable squadrons to declutter?
* Tabs on the side like the settings dialog to group by aircraft type.
* Top tab bar to switch between red and blue air wings.
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