feat(KONFLUX-15176): add SECURITY.md for CRA - #1822

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/github-script@60a0d83039c74a4aee543508d2ffcb1c3799cdea, step-security/harden-runner@a90bcbc6539c36a85cdfeb73f7e2f433735f215b. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/