Added support for AS domain, AS usage type and AS CIDR

Tested with Python 3.13.

Update documentation

Tested with CPython and PyPy

Tested Python 3.12

- Updated setup.py for Python 3.12 compatibility.
- Add gitignore file.

Fix an error saying missing file when running setup.py build

Fix wrong value returned by cidr_to_ipv6 function

Added support for district, ASN and AS.

Added Country and Region class.

Updated the homepage link.

Reduced file I/O.