@bolt/components-critical-css-vars

Note: This package will be removed in Bolt v3.0 when we drop IE11 support, modern browsers support async CSS loading natively. See migrating to Bolt v3.x docs for more info.

Async loads fallback CSS that's automatically generated for browsers that don't natively support CSS Variables.

Also adds support for the Filamentgroup's invaluable [loadCSS])(https://www.npmjs.com/package/fg-loadcss) library to allow CSS to be conditionally loaded.