Update README.md to reflect the fact artefacts are Govspeak now
Update README.md to reflect the fact artefacts are Govspeak now

We used to render regression test artefacts as HTML, but as of
86169cf954dfb72e848439ff8f15f964a053e325 we are generating Govspeak to reduce
unrelated noise in diffs. Reflect this in documentation. Also mention the fact
that landing page artefacts are stored too.

alphagov/smart-answers,aledelcueto/smart-answers,alphagov/smart-answers,alphagov/smart-answers,stwalsh/smart-answers,stwalsh/smart-answers,stwalsh/smart-answers,stwalsh/smart-answers,alphagov/smart-answers,aledelcueto/smart-answers,aledelcueto/smart-answers,aledelcueto/smart-answers