Linear extension for polynomial regression

[FedeClaudi]

Hey everyone,

Thank you for the awesome work with this project.
Here I propose a small change to LinearAnalysis to include x^i terms and allow for polynomial regression.
I currently use this as a separate layer in my own code, but I thought it would be a useful addition to AOG.

Thank you,
Federico

[jkrumbiegel]

Thanks for the PR, just getting to take a look at it now. Could you maybe demonstrate visually what this is supposed to do? I'm not sure what the benefit of x^i terms would be in this context. And we'd need to add an illustrative example to the docs anyway.