fix: use io.ReadFull(rand.Reader, b) in generateRandomBytes - #209

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/add-to-project@v0.5.0. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/