Break up CSS into 'partials'

[ndorfin]

Since the site uses HTTP/2, we can safely break up the CSS into many smaller (and fit for purpose) files, and use @import. 😱

Splitting up the CSS will help with:

• Maintenance
• Inline-splitting for the above-the-fold aspetcs of the homepage (improving performance)
• Theming / Dark-mode support

Regardless of HTTP/2, we could create or use an Eleventy plugin to concat the CSS during build time if we see performance plummet. In light of this, we'll need to capture a baseline metric of the site's performance, and work within a certain threshhold of performance degradation. (if time to first paint performance is 110% of the baseline, we switch to concatting the CSS)

Waddayathink? :D
-S