Update CONTRIBUTING.md for CVE information

Andrew adds new contribution point to email big bang cybersecurity lead for more information on CVEs impacting Big Bang.

requested review from @andrewshoell, @chris.oconnell, @troymobley, @michaelmartin, and @cbowmanclare

assigned to @andrew_vu

approved this merge request

merged

mentioned in commit d5f0f402

changed milestone to %2.41.0