Support for Python 3.12

[aj3sh]

Python 3.12 is scheduled for release in October 2023 and will introduce a variety of new features, optimizations, and bug fixes. It is crucial for our 'nepali' package to keep up with the latest Python version to ensure compatibility and provide the best experience for our users.

This update will enable our users to take advantage of the new capabilities offered by Python 3.12 and ensure that our package remains current within the Python ecosystem.

Action Items:

• Update the project's documentation and README to indicate support for Python 3.12.
• Update the package's dependencies and ensure compatibility with Python 3.12.
• Thoroughly test the package against Python 3.12 to identify and address any potential issues or incompatibilities.
• Update GitHub actions: replace Python 3.9 with Python 3.12.