Release 1.8.0 preparation: changelog + version bump - #1227

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v4, actions/upload-artifact@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

Summary report available at: https://github.com/NeuroTechX/moabb/actions/runs/37455859405#summary-112243175890