Move internal modules to “internal” folder.

.internal/arrayShuffle.js

@@ -0,0 +1,15 @@
+import copyArray from './.internal/copyArray.js';
+import shuffleSelf from './.internal/shuffleSelf.js';
+
+/**
+ * A specialized version of `shuffle` for arrays.
+ *
+ * @private
+ * @param {Array} array The array to shuffle.
+ * @returns {Array} Returns the new shuffled array.
+ */
+function arrayShuffle(array) {
+  return shuffleSelf(copyArray(array));
+}
+
+export default arrayShuffle;