Allow for adding headers to a response in an amphora plugin

[elgreg]

I'd like to be able to attach a list of all the _refs that are on a page (e.g. the article refs for each story card in the home page) as surrogate keys with fastly. @jonwinton suggested adding the ability to add plugins to rendering in amphora. I'd like to hook into the rendering of the homepage in amphora and add surrogate keys for all URLS of linked articles with a Surrogate-Key: header on the HTTP response

[TTaitFoster]

Why not just an express middleware?

[elgreg]

I would prefer that I had access to the components themselves. So maybe this belongs in the renderer?

[jonwinton]

Yes, completely agree. We'll move to amphora-html.

[jonwinton]

Issue moved to clay/amphora-html #57 via ZenHub