prepare 2.15.2 release (#189)

Author: LaunchDarklyCI

.babelrc

@@ -0,0 +1,18 @@
+module.exports = {
+  presets: [
+    [
+      '@babel/env',
+      {
+        targets: ["last 2 versions", "ie >= 10"],
+      },
+    ],
+  ],
+  env: {
+    test: {
+      plugins: [
+        '@babel/plugin-transform-regenerator',
+        '@babel/plugin-transform-runtime',
+      ],
+    },
+  },
+};