Silence "Sass @import rules are deprecated" warning

Requires jekyll-sass-converter >= 3.1.0

Ref: jekyll/minima#815 (comment)

Closes #5026

Author: iBug

_config.yml

@@ -228,6 +228,8 @@ kramdown:
 sass:
   sass_dir: _sass
   style: compressed # https://sass-lang.com/documentation/file.SASS_REFERENCE.html#output_style
+  quiet_deps: true
+  silence_deprecations: ['import']
 
 
 # Outputting