SECURITY: clarify status of parse errors - #58

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: xt0rted/markdownlint-problem-matcher@1a5fabfb577370cfdf5af944d418e4be3ea06f27. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/