Create a new Rabin-Karp Algorithm

[tackhwa]

This is a Rabin-Karp Algorithm for Pattern Searching

Describe your change:

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

References

Rabin–Karp algorithm

Checklist:

• [x] I have read CONTRIBUTING.md.
• [x] I know that pull requests will not be merged if they fail the automated tests.
• [x] This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• [x] All new Java files are placed inside an existing directory.
• [x] All filenames are in all uppercase characters with no spaces or dashes.
• [x] All functions and variable names follow Java naming conventions.
• [x] All new algorithms have a URL in its comments that points to Wikipedia or other similar explanation.