Hydrate clientside

[BookOfGreg]

Fixes #808

Benchmarked on my companies private project and it's significantly faster for us!
Measured using 3 runs of Chrome Lighthouse Audit

I also felt cheeky enough to add myself as an author on the Gem if that's OK.

Rendering Server-side + React.Render (prerendering) faster at Perceptual Speed as it renders server-side but slower at First Interactive as the page is larger

• 4.0s First Interactive
• 2.3s Perceived

Rendering Client-side (no pre-rendering) faster at First Interactive but slower Perceptual Speed as lots of JS used to re-render over the top of more DOM

• 3.0s First Interactive
• 2.7s Perceived

Rendering Server-side + React.Hydrate wins at Both! Faster First Interactive and faster Perceptual Speed as page has content and much less JS to complete it.

• 2.7s First Interactive
• 2.4s Perceived