docs: add the release checklist, the notes composer and a changelog - #18

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/setup-node@1d0ff469b7ec7b3cb9d8673fde0c81c44821de2a. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/