Add an option to support the project through donations

[Su-Well]

This utility is worth much more than $0 for many of its users, so it would be nice to be able to contribute to it by donating. Even if you don't want or need donations right now @RamonUnch, there might be a time when that changes. Accepting financial contributions will allow users to increase the probability that this project will keep being maintained in the future.

[woctezuma]

Relevant thread:

• https://github.com/RamonUnch/AltSnap/issues/149