Rename test fixtures using module syntax to .mjs files.

packages/babel-plugin-transform-function-name/test/fixtures/function-name/modules-2/input.mjs

@@ -0,0 +1,11 @@
+import last from "lodash/last"
+
+export default class Container {
+  last(key) {
+    if (!this.has(key)) {
+      return;
+    }
+
+    return last(this.tokens.get(key))
+  }
+}