Leverage HTTP/2 server push

[housseindjirdeh]

With Firebase, leveraging h2 push seems straightforward which is awesome. Tried this quite some time ago but didn't notice any particular wins, however I do think it's something worth exploring again.

AggressiveSplittingPlugin, although experimental, seems to be a viable solution to output multiple smaller chunks that can be pushed from the server. However, spent a bit of time trying to include it and it doesn't output the generated chunks to the html due to an issue with HTMLWebpackPugin. Definitely something to keep an eye on when this gets resolved.

Open to all kinds of suggestions and tips!