add sass/scratch.scss and associated sass files

Resources/public/sass/contrib/bourbon/functions/_is-length.scss

@@ -0,0 +1,11 @@
+@charset "UTF-8";
+
+/// Checks for a valid CSS length.
+///
+/// @param {String} $value
+
+@function is-length($value) {
+  @return type-of($value) != "null" and (str-slice($value + "", 1, 4) == "calc"
+       or index(auto inherit initial 0, $value)
+       or (type-of($value) == "number" and not(unitless($value))));
+}