Move internal modules to “internal” folder.

.internal/listCacheGet.js

@@ -0,0 +1,19 @@
+import assocIndexOf from './.internal/assocIndexOf.js';
+
+/**
+ * Gets the list cache value for `key`.
+ *
+ * @private
+ * @name get
+ * @memberOf ListCache
+ * @param {string} key The key of the value to get.
+ * @returns {*} Returns the entry value.
+ */
+function listCacheGet(key) {
+  const data = this.__data__;
+  const index = assocIndexOf(data, key);
+
+  return index < 0 ? undefined : data[index][1];
+}
+
+export default listCacheGet;