Python-iso639

Added
* Defined the `LanguageNotFoundError` exception.
* Added support for Python 3.11.

Changed
* If the `Language` class methods `match`, `from_part3`, etc. receive an invalid
input language code or name, a `LanguageNotFoundError` is now raised.
(Previously, `None` was returned with no exception raised.)

Removed
* Dropped support for Python 3.7.

Added
* Added constants `DATA_LAST_UPDATED` and `ALL_LANGUAGES`.

Fixed
* Corrected repo name in package metadata and documentation.

* First release!