Move internal modules to “internal” folder.

.internal/baseForOwn.js

@@ -0,0 +1,16 @@
+import baseFor from './.internal/baseFor.js';
+import keys from './keys.js';
+
+/**
+ * The base implementation of `forOwn`.
+ *
+ * @private
+ * @param {Object} object The object to iterate over.
+ * @param {Function} iteratee The function invoked per iteration.
+ * @returns {Object} Returns `object`.
+ */
+function baseForOwn(object, iteratee) {
+  return object && baseFor(object, iteratee, keys);
+}
+
+export default baseForOwn;