Choose adaptive icon shape

[Commenter25]

Adaptive icons can be masked into any desired shape. It would be nice to choose between a circle, square, rounded square, or squircle.

To be clear, a squircle is not exactly a rounded square, but rather between a square and a circle, like this:

[peterfajdiga]

This would be a nice feature to have, but I don't have the spare time to implement nice to have, but lower priority features. :(
I don't want to close this issue, so I'm creating a new label for issues like this.