Polygon support

[firegloves]

I'm trying to adapt the project to target the polygon network.
I'm progressing with difficulty, discovering that some data about the mainnet or rinkeby is hardcoded across some project files (e.g. mint.js file).

Currently, it is not clear to me if I have to update the file 2_deploy_contracts.js by supplying a different proxy registry address (maybe the one reported here?)

Can you please apply the changes required in order to support polygon out of the box? Otherwise is there a guide that I can follow?

[stpoa]

@firegloves have you managed to deploy to Polygon?