added demo site

demo/css/main.css

@@ -0,0 +1,7 @@
+@import './reset.css' layer(reset);
+@import './custom_properties.css' layer(custom-properties);
+@import './tags.css' layer(tags);
+@import './grid.css' layer(grid);
+@import './utility_classes.css' layer(classes);
+
+@import './fonts.css';