Add usage example in README file

[yeshuawm999]

Describe your change:

Added a new Usage Example section to the bottom of the README file.

This section explains how users can clone the repository, run algorithms locally, use the interactive Python shell, and run doctests.
It helps beginners quickly understand how to execute algorithms from the project.

Fixes #13714

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• [ ] Add an algorithm?
• [ ] Fix a bug or typo in an existing algorithm?
• [ ] Add or change doctests?
• [x] Documentation change?

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Checklist:

• [x] I have read CONTRIBUTING.md.
• [x] This pull request is all my own work.
• [x] I know that PRs will not be merged if automated tests fail.
• [x] This PR changes only the README documentation file.
• [x] The Markdown style follows the repository’s format and emoji section headers.
• [x] Includes a clear “Usage Example” section for readers.