Tutorial for shape optimization of a multilayer stack (NanoComp#2862)

* simulation script for adjoint gradient of a multilayer stack with respect to layer thicknesses

* add 0.5 correction factor to adjoint gradient as well as docstrings

* switch optimization problem from single wavelength to multi wavelength (minimax)

* add text and figures

* add figures

* minor tweaks and fixes to text

* update figures with new design

* update script, text, and two figures with new results and add schematic of design problem

* Update doc/docs/Python_Tutorials/Adjoint_Solver.md

* Update doc/docs/Python_Tutorials/Adjoint_Solver.md

* Update doc/docs/Python_Tutorials/Adjoint_Solver.md

* Update doc/docs/Python_Tutorials/Adjoint_Solver.md

* Update doc/docs/Python_Tutorials/Adjoint_Solver.md

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Co-authored-by: Steven G. Johnson <[email protected]>