WIP: Add typescript typings

[marvinhagemeister]

This PR adds typing so that the styled function will type-check when using typescript.

Still marked as wip because somehow the template tags are not recognized yet

Fixes #40

[codecov-io]

Codecov Report

Merging #37 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #37   +/-   ##
=======================================
  Coverage   87.54%   87.54%           
=======================================
  Files          15       15           
  Lines         530      530           
  Branches      107      107           
=======================================
  Hits          464      464           
  Misses         53       53           
  Partials       13       13

Impacted Files	Coverage Δ
src/styled.js	100% <ø> (ø)	⬆️

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[tkh44]

This may need a name change. I plan on adding a Style component in the future and this might get confusing. If this is how styled-components looks though then I say leave it.

[tkh44]

I'm not really familiar with typescript so I'm going to have to rely on external reviewers on this. I trust you, @patrick91, and others can work together on this 👍

[A-gambit]

@marvinhagemeister Hey can you update your pull with the latest version of emotion?

[tkh44]

I'm going to close this for #379