docs: add avivdon as a contributor for security

[allcontributors]

Adds @avivdon as a contributor for security.

This was requested by iluwatar in this comment

[skip ci]

[github-actions]

PR Summary

Adds avivdon as a contributor for security. This was requested by iluwatar in the linked comment. Updates All Contributors configuration and README badge/table accordingly.

Changes

File	Summary
.all-contributorsrc	Appended a new contributor entry for avivdon with login avivdon, name avivdon, avatar_url https://avatars.githubusercontent.com/u/74790003?v=4, profile https://github.com/avivdon, and security contribution.
README.md	Updated All Contributors badge to 397 and added a new contributor cell for avivdon under the security column, including avatar, name, and profile.

---

autogenerated by presubmit.ai

[github-actions]

✅ LGTM!

Review Summary

Commits Considered (2)

• 1adf50b: docs: update .all-contributorsrc [skip ci]
• e983834: 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 [3615-3623]

  maintainability: "Add new All Contributors entry for security"

• README.md [9-9]

  readability: "Update All Contributors badge count"

• README.md [591-593]

  readability: "Add avivdon to security table"