Improve Boyer-Moore String Search (Bad Character Rule) Implementation - #13039

Describe your change:

• Fix a bug or typo in an existing algorithm
• Add or change doctests
• Documentation change

This PR improves the Boyer-Moore string search (bad-character rule) implementation:

• Added a functional API boyer_moore_search(text, pattern) alongside the class wrapper for compatibility.
• Precomputed a bad-character table for O(1) lookup per mismatch.
• Corrected shifting logic with a while-loop (avoiding overwriting i).
• Handled edge cases (empty text, empty pattern, pattern longer than text).
• Allowed overlapping matches.
• Expanded doctests to include typical and edge cases.
• Preserved BoyerMooreSearch class for backward compatibility.
• Improved documentation and clarity.

As per guidelines, no issue was raised before this PR since algorithm contributions should go directly as PRs.
This contribution is part of Hacktoberfest 2025 🎉

Checklist:

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, separate algorithms would be separate PRs.
• All new Python files are placed inside an existing directory.
• All filenames are in all lowercase characters with no spaces or dashes.
• All functions and variable names follow Python naming conventions.
• All function parameters and return values are annotated with Python type hints.
• All functions have doctests that pass the automated testing.
• All new algorithms include at least one URL that points to Wikipedia or another similar explanation.