docs: add SandhyaDevadiga as a contributor for code

[allcontributors]

Adds @SandhyaDevadiga as a contributor for code.

This was requested by iluwatar in this comment

[skip ci]

[github-actions]

PR Summary

Adds @SandhyaDevadiga as a contributor for code; updates All Contributors config and README badge/table accordingly.

Changes

File	Summary
.all-contributorsrc	Add a new contributor entry for SandhyaDevadiga with login, name, avatar_url, profile, and a code contribution.
README.md	Update All Contributors badge count (to 415) and add Sandhya to the contributors table in the acknowledgments.

---

autogenerated by presubmit.ai

[github-actions]

✅ LGTM!

Review Summary

Commits Considered (2)

• a926697: docs: update .all-contributorsrc [skip ci]
• cf06f5b: docs: update README.md [skip ci]

Files Processed (2)

• .all-contributorsrc (1 hunk)
• README.md (2 hunks)

Actionable Comments (0)

Skipped Comments (3)

• .all-contributorsrc [3776-3785]

  enhancement: "Add contributor to All Contributors config"

• README.md [9-9]

  enhancement: "Update All Contributors badge"

• README.md [616-618]

  readability: "HTML table structure for contributors"