Libgolf

None

- add `List.integers`, the infinite list `1, 2, 3, ...`
- add `List.powerset` and `List.prefixes`
- make `List` slicing and boolean testing lazier
- make `List.exhaust` return `self`, making chaining more convenient

**Full Changelog**: https://github.com/pxeger/libgolf/compare/v0.0.2...v0.0.3