Add pylings to the Rustlings third-party exercises list

[abhiksark]

Part of the 0.3.0 adoption roadmap — Discovery.

Why (adoption impact)

Rustlings' README maintains a list of "third-party / other-language" ports (golings, ziglings, etc.). People who loved Rustlings and want the same for Python are our highest-intent audience — and they look here.

Scope / acceptance criteria

• Find the relevant section in https://github.com/rust-lang/rustlings (README "Third-party exercises" / community list) and confirm its inclusion criteria.
• Open a PR adding pylings (python-learnings) with a one-line description and repo link.
• If they require a separate community list/issue rather than README edits, follow that path instead.
• Link the PR/issue back here.

Difficulty

good first issue · help wanted — external PR, ~30 min.