Update to style-components v4

[gabimoncha]

I think this package will benefit a lot if it is updated to styled-components v4

[diegomura]

Thanks! I'm not that familiar with v4 changes. Could you explain a bit further why you think is that?

[gabimoncha]

From what I understand v4 is smaller, but also mounts faster due to some refactoring and optimisations around memory usage and JS engine implementation details.

[diegomura]

Ok. Sounds good!
I'll try to take a look at this soon, but I still have some other issues to tackle before this 😅 .
Feel free to jump on this if you like!

[gabimoncha]

One nice issue that I can't do, is the support of SVGs for react-pdf :)

[diegomura]

I just checked this, and it wouldn't be that simple to implement. The main cause is that styled-components v4 does not export the lib dir but just the bundles. I'm not going to work on this in the near future, so if someone feels like tackling this, please do!