Update GlobalStyle to utilize Polished Normalize

[designmatty]

Currently, our GlobalStyle is a copy-paste from normalize.css. This is problematic in that this requires manual updates as new "normalizations" are defined.

As it happens, one of our dependencies, polished.js, can handle this for us. https://polished.js.org/docs/#normalize

I propose we remove our copy-paste and replace it with the above method. Note, we should maintain our themeable attributes.