Mode-superposition transient analysis, with mode selection for expansion

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📝 Description of the example

Add an example of a Mode Superposition Transient Analysis:

• show data source creation, scoping in time, on mesh...
• add a final section on selection of modes for the expansion, which showcases use of operators modal_basis and modal_superposition.

📁 Files needed for running the example

Add example files related to a MSUP transient analysis.

[PProfizi]

@rajesh1359