Headless rendering of webpages for dynamically inserted JSON+LD

[justinccdev]

Unfortunately, from recent discussion, it's becoming clear that some sites are very reluctant to render their JSON+LD statically. Therefore, we need to look at whether rendering in a headless browser is feasible from a performance perspective, particularly when we may be crawling 10s of millions of webpages.

@ricardoaat is looking into this, so we can wait for more information on feasibility before looking to do this in buzzbang-ng