Pin dependency classnames to 2.2.6 (#313)

Author: renovate[bot]

package-lock.json

@@ -39,7 +39,7 @@
     "babel-core": "7.0.0-bridge.0",
     "babel-eslint": "10.0.1",
     "babel-loader": "8.0.5",
-    "classnames": "^2.2.6",
+    "classnames": "2.2.6",
     "clean-webpack-plugin": "1.0.0",
     "core-js": "2.6.2",
     "cross-env": "5.2.0",