FIX: render Plotly again on notebook pages

[redeboer]

• Downgrading Plotly to v5
• Closes Ploly plots not shown on website #36, see TR-006, TR-023, TR-025, TR-026, and TR-027
• Remove from __future__ import annotations from notebooks
• Replace %config InlineBackend.figure_formats with set_matplotlib_formats() call
• Use rasterized=True instead of PNG figure format
• Test notebooks on GitHub Actions when they or their dependencies are modified
• Use cmap="coolwarm" instead of cmap=plt.cm.coolwarm
• Make all notebooks runnable again by addressing dependency issues (apart from TR-011)