Add support for hosted option through Google Fonts

[joshblack]

As part of our IBM Plex for v11, we added support for using fonts directly from the @ibm/plex package. However, we would like to keep our hosted option available that is available in v10. This will help teams migrate from v10 to v11 and also provides an alternate setup out-of-the-box when using Carbon.

The default behavior in v11 will be to use fonts directly from @ibm/plex, to enable hosting we should support a flag in the config package that enables hosted fonts and disables custom @font-face blocks from the package.

The difference between hosted and non-hosted is simply the value of the url() in the @font-face block. Most likely we could use our resolver to implement the logic for getting the correct url path when hosted is set to true in config.