Move internal modules to “internal” folder.

.internal/createSet.js

@@ -0,0 +1,17 @@
+import setToArray from './.internal/setToArray.js';
+
+/** Used as references for various `Number` constants. */
+const INFINITY = 1 / 0;
+
+/**
+ * Creates a set object of `values`.
+ *
+ * @private
+ * @param {Array} values The values to add to the set.
+ * @returns {Object} Returns the new set.
+ */
+const createSet = (Set && (1 / setToArray(new Set([,-0]))[1]) == INFINITY)
+  ? values => new Set(values)
+  : () => {};
+
+export default createSet;