Link header for server push

[rugk]

It would be nice if you could set link headers for pushing assets to the user. Especially the HTTP/2 server push is an efficient way of doing that and it really speeds up website loadings.

However I know that only static files are loaded are requested. Therefore you may only be able to use this problem in the webserver config. Basically you need to add some Link headers sent when /index.html is requested. For this a configuration example/list of headers to send would be useful. As the assets may change it might be useful to integrate this into the build script.

[Gaff]

Hmm - definitely nice-to-have territory. If someone wants to submit a pull request then great, but otherwise I've so little time for this anyway :(