Corrected git history: Adding requirements.txt, pre-commit-hook and allowing higher python version

[ShantanuKodgirwar]

@roflmaostc @wfeschen

Resending this PR as the commit history was incorrect for the last one.

After discussion with @wfeschen, we decided that it makes sense to add a requirements.txt file for using exact dependencies for development instead of being more flexible which is useful when using PtyLab as a dependency in another project.

This PR adds the following:

• poetry.lock file for exact dependency usage for development
• requirements.txt file created from poetry.lock file that can be used for installing via pip.
• When a dependency is modified, the lock file changes, by adding the pre-commit hook under .pre-commit-config.yaml based on Poetry, it syncs the lock file with the requirements.txt file + some additional checks.
• The details of using the pre-commit hook when using Poetry for package management are added under CONTRIBUTING.md
• README.md is now modified by specifying the use of the requirements file for development.
• Now we allow for python < 3.13 (earlier was 3.12) for higher flexibility.
• version change to 0.2.1

I have tested this with and without GPU, with and without poetry for covering all test cases. So this can be merged without issues.

[roflmaostc]

Thanks, good work :)