This introduces improvements for XBlock interactions within iframes: * Add default styles for Library Content that renders in the iframe in the new Studio unit page * When the `isIframeEmbed` option is enabled, the XBlock sends a `postMessage` to the parent window. When sending such a message, the standard link transition is cancelled and the transition is carried out in the MFE.
Sass Watch: sass --watch cms/static/sass:cms/static/sass -r ./cms/static/sass/bourbon/lib/bourbon.rb