Creates CSS output and adds to Processor object from SCSS in other plugins
Uses the Dart CASS program to convert SCSS input into CSS output that is added to the RPO structure.
The plugin is intended to be run once and after any other plugin that defines a scss: field in its %.config attribute in the correct manner for HTML-Extra, eg.,
%!config =
:scss( [ self.add-scss-string, 2], ),
The scss attribute must be a sequence of Str,Int tuples, so the comma inside the ) is important.
It is assumed that a shell call to sass -v will yield a version number, otherwise the plugin will die.
Note that a plugin can be disabled by overriding the default plugin list (see Customisability in HTML-Extra ).