Move internal modules to “internal” folder.

.internal/baseCreate.js

@@ -0,0 +1,30 @@
+import isObject from './isObject.js';
+
+/** Built-in value references. */
+const objectCreate = Object.create;
+
+/**
+ * The base implementation of `create` without support for assigning
+ * properties to the created object.
+ *
+ * @private
+ * @param {Object} proto The object to inherit from.
+ * @returns {Object} Returns the new object.
+ */
+const baseCreate = (() => {
+  function object() {}
+  return proto => {
+    if (!isObject(proto)) {
+      return {};
+    }
+    if (objectCreate) {
+      return objectCreate(proto);
+    }
+    object.prototype = proto;
+    const result = new object;
+    object.prototype = undefined;
+    return result;
+  };
+})();
+
+export default baseCreate;