describe requires-python fallback in docs

[dylwil3]

Adds description of requires-python fallback to documentation for configuration file discovery.

[codspeed-hq]

CodSpeed Performance Report

Merging #16704 will not alter performance

_{Comparing dylwil3:config-docs (8da82b6) with main (abaa189)}

Summary

✅ 32 untouched benchmarks

[github-actions]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

✅ ecosystem check detected no linter changes.

[MichaReiser]

Thanks, this looks good

[MichaReiser]

I'll change the base. We can merge this directly into main.

[ntBre]

This looks great, and thanks for adding the subsection!

My only quibble is with the second rule. It seems slightly confusing to me, but I think it would be too verbose to try to add ruff.toml (or especially a list of file options) in place of each "configuration[ file]" occurrence to clarify things.

[dylwil3]

My only quibble is with the second rule. It seems slightly confusing to me, but I think it would be too verbose to try to add ruff.toml (or especially a list of file options) in place of each "configuration[ file]" occurrence to clarify things.

Yeah I agree it's a bit awkward, but I can't think of a better way to word it at the moment. It's especially confusing because the found configuration file could itself be a pyproject.toml, just one that's missing both requires-python and target-version.

[ntBre]

Agreed, I think it's good for now. We can iterate if users actually get confused.