fix(history-chart): show gaps for missing data instead of connecting lines - #150

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@v1.0.2. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/