feat: Add auto-generated UML diagram to docs

[igopalakrishna]

Fixes #52

This pull request adds a UML class diagram to the main documentation page to help developers understand the project's code architecture.

Key Changes:

• Automation: A new pre-commit hook was added to .pre-commit-config.yaml to automatically generate the diagram using pyreverse and graphviz.
• Makefile: The generation logic is encapsulated in a new make uml command in the Makefile.
• Documentation:
  • The generated diagram is now displayed on the docs/index.md page.
  • The docs/setup.md guide was updated to include graphviz as a required development dependency.

• Tests pass
• Appropriate changes to documentation are included in the PR

[s2t2]

As discussed, it would be nice to simplify the diagram (removing some of the details about parameters of each class), and orient it vertically (so we can perhaps include it in the documentation site).

Also, the pre-commit hook is nice, but depending on how long it takes to run, we might prefer a more manual or occasional update process, to streamline the developer experience. Manual process might be fine, otherwise perhaps a GitHub action that runs once a month and creates a PR if there are any updates to the diagram.