✨ Implement spectrotemporal models as implemented in paramGUI

[joernweissenborn]

A spectrotemporal model for fitting time-resolved spectroscopy data is described in the paper
Global and target analysis of time-resolved spectra DOI: 10.1016/j.bbabio.2004.04.011

A public implementation is available in the R package paramGUI.

This issue is about implementing equivalent functionality, but implemented using megacomplex composition.

A repository for validation example code can be found here: pyglotaran-validation this contains the (reference) paramGUI examples to test the implantation against.

[jsnel]

This has been implemented on staging. Validation of functionality was performed using scripts found in the pyglotaran-validation repository.

Issue should be closed when staging is merged to main, see: #777

[jsnel]

Staging was merged into main with #778 so it's in, and it was validated against paramGUI.