Update README.md: Added uv section

[davidhedlund]

Proposed change

• There is an inconsistency in the documentation: the GitHub README states that pip should be used but does not mention uv. Conversely, the ReadTheDocs Examples page recommends using uv instead of pip. We should align these to avoid confusing users.
• On Debian and Ubuntu distributions, pip is not pre-installed, and pip3 requires manual installation along with the --break-system-packages flag to run. Using uv bypasses these hurdles completely with a simple, hassle-free installation.

Partially fixes:

• README.md: Add uv, and git sections #3670

Your PR description goes here.

Type of change

• New country/market holidays support (thank you!)
• Supported country/market holidays update (calendar discrepancy fix, localization)
• Existing code/documentation/test/process quality improvement (best practice, cleanup, refactoring, optimization)
• Dependency update (version deprecation/pin/upgrade)
• Bugfix (non-breaking change which fixes an issue)
• Breaking change (a code change causing existing functionality to break)
• New feature (new holidays functionality in general)

Checklist

• I've read and followed the contributing guidelines.
• I've run make check locally; all checks and tests passed.

[coderabbitai]

Walkthrough

The README's "Install" section is replaced with a new "Installation & execution" section, splitting instructions into pip-based and uv-based installation and execution paths, including quick-run and script usage examples.

Changes

README Installation Docs

Layer / File(s)	Summary
Pip installation and quick run instructions README.md	Adds pip stable install/update, GitHub dev install, dev-to-main note, and a CLI quick-run example replacing the old "Install" section.
Uv installation and execution instructions README.md	Adds uvx one-off execution instructions and examples for interactive shell and local script usage with holidays.

Estimated code review effort: 1 (Trivial) | ~3 minutes

Related PRs: None identified.

Suggested labels: documentation

Suggested reviewers: None identified.

Poem: A rabbit hops through docs anew, / Pip and uv, both in view. / Install, quick-run, a script to try, / README's clearer, no need to sigh.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title matches the main change: adding a uv section to the README.
Description check	✅ Passed	The description is clearly related to the README installation update and the uv documentation change.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[cubic-dev-ai]

No issues found across 1 file

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

_{Re-trigger cubic}

[KJhellico]

• There is an inconsistency in the documentation: the GitHub README states that pip should be used but does not mention uv. Conversely, the ReadTheDocs Examples page recommends using uv instead of pip. We should align these to avoid confusing users.

There's no inconsistencies here. You're mixing recommendations for a user who needs a library (developer) with those for a user who just needs a tool to generate iCalendar files. And when I said that uv should be mentioned, I simply meant that it would be helpful to mention uv add holidays alongside pip install holidays for those who use uv.