Fix for css class names with escaped characters

[EvanLovely]

OK, this should fix the situation where css classes like .u-hide\@large get turned into .u-hide-large until the bug in css-loader can get fixed. /cc @sghoweri

Jake, can you check to see if this fixes the issue, then merge if it does?

[EvanLovely]

Well, crap; getting this build error:

-theAtSymbol- is the temp string I was transforming it to and from.

Error: /home/travis/build/bolt-design-system/bolt/packages/global/styles/index.scss
Module build failed: ModuleBuildError: Module build failed: Unknown word (1:1)
> 1 | -theAtSymbol-charset "UTF-8";
    | ^
  2 | @font-face {
  3 |   font-family: OpenSansSubset;
  4 |   src: url(/fonts/opensans-subset.woff2) format("woff2"),url(/fonts/opensans-subset.woff) format("woff");

My initial tests were just on my small use case, not on the whole thing.

[EvanLovely]

I've done some more research on the core issue and posted some findings in comments there. Also, I've found that disabling CSS Modules with modules: false also gets the behavior we want w/o this workaround. Are we using them?