Moving "to the top" the @import CSS rule

This commit solves a bug that prevents Fonts to properly load and be
shown.

As per the CSS2.1 / CSS3 standard: "Any ‘@import’ rules must follow
all ‘@charset’ rules and precede all other at-rules and rule sets in
a style sheet."

see the standards and/or https://developer.mozilla.org/en-US/docs/CSS/@import