Implement Rabin-Karp algorithm for substring search

[nayan458]

Summary

This PR introduces the Rabin-Karp algorithm for substring search in Java. It includes:

• RabinKarpSubstringSearchSnippet class with:
  • rabinKarpSearch method to find the first occurrence of a substring.
  • Efficient hash computation using a large prime.
  • Sliding window hash recalculation.
  • Substring equality check for collision handling.
• RabinKarpSubstringSearchSnippetTest class similar to the tests in KMP for testing and comparisons.
• A ready-to-use README.md snippet documenting usage.
• BUILD SUCCESSFUL

Benefits

• Provides an alternative to KMP for substring search.
• Suitable for multiple pattern searches with rolling hash.
• Modular, clean, and well-documented code for educational and production use.

Notes

• Uses 1_000_000_007 as prime to reduce hash collisions.
• Designed for clarity and maintainability.