Move internal modules to “internal” folder.

.internal/baseFor.js

@@ -0,0 +1,16 @@
+import createBaseFor from './.internal/createBaseFor.js';
+
+/**
+ * The base implementation of `baseForOwn` which iterates over `object`
+ * properties returned by `keysFunc` and invokes `iteratee` for each property.
+ * Iteratee functions may exit iteration early by explicitly returning `false`.
+ *
+ * @private
+ * @param {Object} object The object to iterate over.
+ * @param {Function} iteratee The function invoked per iteration.
+ * @param {Function} keysFunc The function to get the keys of `object`.
+ * @returns {Object} Returns `object`.
+ */
+const baseFor = createBaseFor();
+
+export default baseFor;