Add preact-emotion

[emmatown]

What:

Add a preact-emotion package with react aliased to preact

Why:

We only use createElement from react which preact exports but most people have react aliased to preact-compat so it's included anyway even if it's not needed.

How:

Add a rollup config that aliases react to preact.

Checklist:

• Documentation
• Tests N/A I don't really think we need tests for this since we only use createElement and there isn't any seperate src
• Code complete

[codecov-io]

Codecov Report

Merging #273 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #273   +/-   ##
=======================================
  Coverage   90.37%   90.37%           
=======================================
  Files          21       21           
  Lines         966      966           
  Branches      260      260           
=======================================
  Hits          873      873           
  Misses         75       75           
  Partials       18       18

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