Completion of the SciML Documentation Overhaul

[ChrisRackauckas]

The following are the major steps to complete the SciML documentation overhaul:

• [x] Finish fixing up the materials for the SciML workshop (https://github.com/SciML/SciMLWorkshop.jl/pull/7), and add it to the SciML docs
• [x] Add the SciML workshop to the landing page of the SciML docs, and to the Github organization README
• [ ] https://github.com/SciML/SciMLDocs/issues/104
• [x] https://github.com/SciML/SciMLDocs/issues/106
• [x] Finish writing Integrals tutorial for SciML getting started (me)
• [x] Finish writing fitting tutorial for SciML getting started (me)
• [x] https://github.com/SciML/SciMLDocs/issues/93 (me)
• [x] Turn DiffEqGPU doc examples into runnable
• [x] Turn HighDimPDE doc examples into runnable
• [x] Turn DeepEquilibriumNetworks doc examples into runnable
• [x] Setup SciMLSensitivity like https://github.com/SciML/ModelingToolkit.jl/pull/1993 (me)
• [ ] Convert each example of https://github.com/ChrisRackauckas/universal_differential_equations into examples for SciMLSensitivity
• [x] Simplify the getting started page of DifferentialEquations by using the tips in https://github.com/SciML/ModelingToolkit.jl/pull/1993 (me)

[ChrisRackauckas]

Turn DeepEquilibriumNetworks doc examples into runnable

@avik-pal can you try to do that within the next week?