audit: no plugins about lighthouse

[samccone]

👍 I like this idea

---

We should think about adding a CSP gatherer, or a CSP audit --- not sure if this will sit ontop of the HTML gatherer or if we can be smarter about it.

[paullewis]

Definitely like this idea. Looking into CSP stuff to see what we can do.

[paullewis]

Okay, so @mikewest says in the longer term we may have https://w3c.github.io/webappsec-csp/api/ to play with, for now I'll roll with checking the headers. Which I think we should be able to do from the existing Network records gather.

[paulirish]

dupe of #3180 now.