Add karatsuba

[adesh2756]

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized it.
• All filenames are in PascalCase.
• All functions and variable names follow Java naming conventions.
• All new algorithms have a URL in their comments that points to Wikipedia or other similar explanations.
• All new code is formatted with clang-format -i --style=file path/to/your/file.java

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 75.24%. Comparing base (ce314e1) to head (ea7f832).
⚠️ Report is 8 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #6569      +/-   ##
============================================
+ Coverage     75.16%   75.24%   +0.08%     
- Complexity     5595     5627      +32     
============================================
  Files           688      691       +3     
  Lines         19361    19448      +87     
  Branches       3744     3758      +14     
============================================
+ Hits          14552    14633      +81     
- Misses         4245     4248       +3     
- Partials        564      567       +3     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.