Adding Python package structure

[amit-sharma]

Adding a standard python package structure to the repo so that it can installed by pip or poetry.

• Renamed suggesters folder to be the same as the PyPI package name (pywhyllm without the hyphen)
• Included pyproject.toml with package description and dependencies
• Included CONTRIBUTING.md and GOVERNANCE.md from PyWhy.
• Included MAINTAINERS.md as @emrekiciman and @amit-sharma.
• Included a placeholder docs/source/ folder.