Move internal modules to “internal” folder.

.internal/arrayEach.js

@@ -0,0 +1,21 @@
+/**
+ * A specialized version of `forEach` for arrays.
+ *
+ * @private
+ * @param {Array} [array] The array to iterate over.
+ * @param {Function} iteratee The function invoked per iteration.
+ * @returns {Array} Returns `array`.
+ */
+function arrayEach(array, iteratee) {
+  let index = -1;
+  const length = array == null ? 0 : array.length;
+
+  while (++index < length) {
+    if (iteratee(array[index], index, array) === false) {
+      break;
+    }
+  }
+  return array;
+}
+
+export default arrayEach;