Add chsh example

[blegat]

@kalmarek I'll wait for KnuthBendix to integrate Monoids before merging this, I'll leave it as a WIP for now. I needed a workaround with Full for it to work with the KernelBridge, it's not ideal as it is ignoring the MTable. Maybe it would be resolved by something similar to: https://github.com/JuliaAlgebra/StarAlgebras.jl/pull/55

Closes https://github.com/jump-dev/SumOfSquares.jl/issues/364