Make TACOCAT installable

From @veeshy - https://github.com/veeshy:

"Structure looks good for the scope the original article mentioned. Next good steps would be to make the project installable so you can import it from anywhere, [pyproject-toml](https://pip.pypa.io/en/stable/reference/build-system/pyproject-toml/) and that would lead nicely into using GitHub-actions to setup [automated tests](https://docs.github.com/en/actions/automating-builds-and-tests/building-and-testing-python)"

Review the repository structure and current Python import layout, then read the linked pyproject.toml documentation to identify the packaging metadata and build configuration needed. Done means the project can be installed and imported from outside the repository; automated GitHub Actions tests are described as a later follow-up rather than part of this issue.

Written by the indexing model from the issue text.