Configured headers not passed through to rendering

[mcon]

Some usecases of rendering with JS require headers from the initial request to be passed through to the rendering engine - inspecting the requests made by the headless chrome instance, it doesn't look like these get passed through.

In particular, calling setExtraHTTPHeaders on the pyppeteer.Page object which does the rendering looks like it should do the trick.

At the very least, I think this would be a useful optional feature.