maxR overlapping orbitals or in its own radius

[zerothi]

Maybe there could be two categories, an "overlaps" for the overlap situation, and a "neighborhood" where R then should be specified? I think this would cover the relevant use cases.

Originally posted by @jonaslb in https://github.com/zerothi/sisl/pull/218#issuecomment-628836410

The problem is that maxR is currently used as a fixed radius of interaction. However, orbitals that overlaps interact and thus it would be more natural to use maxR * 2 (if they have the same maxR) to calculation interactions.