Inline CSS fixes

[prateekbh]

To be merged after: GoogleChromeLabs/critters#45

What kind of change does this PR introduce?
Bug fix

Did you add tests for your changes?
Updated the existing tests

Summary
Critters only inlines the css from the css files actually present in the html.
This was the reason why home page's css was never inlined on http://cli-demo-next.preactjs.com
This PR adds route's css as well as bundle css

Does this PR introduce a breaking change?
No

[prateekbh]

Ahhh problem!
We always pre-render home, which means for someone who points all routes to / there will always be extra css loaded via route-home.chunk.css

[ForsakenHarmony]

for someone who points all routes to /

wdym?

[prateekbh]

Like deploy to surge and redirect * to /

[ForsakenHarmony]

Oh you're talking about the backend always serving /index.html, not the route specific html files

[prateekbh]

yep, in that case all routes will download an extra route-home.chunk.xxxxx.css

[prateekbh]

// @developit: ^ request for additional stylesheets options in critters