support for headless WordPress + remote Next.js frontend

[jessuppi]

I'm not sure what this would look like exactly but I'm going to open this Issue while I'm thinking about it again, it would be nice to explore better support in SlickStack for headless WordPress if possible, whatever that might entail.

[jessuppi]

Relevant new doc here: https://github.com/littlebizzy/slickstack/blob/master/docs/headless.md