Backport of datetime.fromisoformat

This library provides a backport of Python 3.11's extended `datetime.fromisoformat` functionality to older Python versions (prior to 3.11). It allows parsing a wider range of ISO 8601 formatted strings, including those with timezone offsets using colons and fractional seconds. The current version is 2.0.3, with releases occurring on an as-needed basis to address compatibility or new Python version changes.