Streaming HTML payload

[PEM--]

• Reconstruct HTML payload with async links via WebApp.clientPrograms['web.browser']
• Add streaming capability to Express with express-stream

[cbilotta]

React server-side rendering in version 16.00 now allows us to stream the HTML while it is generated. That would be a nice addition for when the cache is not already filled.

EDIT : It will cause problems with styled-components.