Cachetoolsutils

- Simpler and more compact json cache key function.

- Improve documentation.
- Add experimental `json_key` and `hash_json_key` cache key functions.

- Add `stats` method to return a convenient `dict` of statistics.
- Improve type declarations.
- Add some tests.
- Test with (future) Python 3.14.
- Fix doc typo.

- Add license section to README.
- Add `ruff` pass.
- Add _Pypy 3.10_ and _Python 3.13_ to CI.

- improved typing
- updated CI

- improved doc
- improved type checking