Inline <style> elements violates style-src Content Security Policy

[jelbourn]

See https://developer.mozilla.org/en-US/docs/Web/Security/CSP/CSP_policy_directives#style-src

In order to address this, there would need to be build-time tooling to let people generate their own theme css outputs.

[epelc]

Would be nice if there was also a gulp plugin for this