In continuation of the previous change, prepend `Store` to the name to
specify the difference.
The goal is to add `StoreDetailsWidget` as a second view in `GameDetails`
with information sourced from the Epic Games Store.
* Add a big back button in details page.
* Add static CSS to render QPushButtons as flat when the `flat` property is set
* Remove outer scroll areas from details page since the page is already adjustable
* Remove scroll area from the requirements widget because ElideLabels are already used in it.
* Fix crash when sorting the wishlist
