Update and pin actions. Update node-version for release-please. - #198

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: denolib/setup-deno@4df079f84f6c4ef488b04806df9af59e51d09bfb. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/