Improvements & general refactoring

[AA-Turner]

To allow python/cpython#129120, we need to introduce the ability to have a different URL base for social card images to the canonical URL.

In preparation to start this work I have made some general improvements to the codebase, which are described in each commit. I would suggest rebase-merging or fast-forward merging to maintain understandable history.

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4388f9e git mv setup.py pyproject.toml
173cfc8 Use declarative metadata

Closes #44. Move from the deprecated setup.py to the standardised pyproject.toml, maintaining git history by git mving the file first. We also fix a markup error in LICENCE.md, as it is declared to be a markdown file.

6cf22f2 Support READTHEDOCS_CANONICAL_URL

Closes #129. Read the Docs no longer inject html_baseurl.

07ae701 Declare support for Python 3.13

Closes #131. Python 3.13 was released in October last year.

4be7f53 Improve performance of get_title()

We don't need to call the method twice, we can just return both strings and use tuple unpacking.

3f99ead Define a social_cards optional extra

CLoses #112. This makes the feature more discoverable.

d400791 Use pathlib in tests

Closes #111. sphinx.testing.path is deprecated.

c161663 Sort imports

Linting.

2cff296 Improve performance of get_description()

We use a membership test with in, so we should use a set rather than a list.

e416bc5 Drop support for Python 3.8
c75cafb Drop support for Sphinx 5

Reduces the support matrix. Python 3.8 is end-of-life. I would also suggest dropping Python 3.9, but that is more arguable. Sphinx 5 was released three years ago.

4328637 Adopt Ruff
7f3c66a Enable Ruff linters

Ruff is a fast linter and formatter that has wide adoption, including in Sphinx and CPython.

26cfaf4 Improve type annotations

Type annotations are useful in IDEs such as PyCharm, and for downstream projects.

d78b198 Factor out social_card_for_page()
117abcb Fix config type in get_tags()
43d177c Avoid passing the app object around
a5e22d3 Factor out read_the_docs_site_url()

Miscellaneous refactoring to make functions smaller and arguments more explicit.

8c7a7cf Enable more linter categories in Ruff

Enable more categories beyond general correctness, including requiring that every function is annotated and ensuring imports aren't redundantly aliased (fixing e.g. import docutils.nodes as nodes).

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cc @ItayZiv @TheTripleV @Daltz333 @sciencewhiz

A