Add missing top-level dev dependency

Author: sarayourfriend

package.json

@@ -170,6 +170,7 @@
 		"csstype": "^3.0.10",
 		"deep-freeze": "0.0.1",
 		"enzyme": "3.11.0",
+		"enzyme-to-json": "^3.4.4",
 		"equivalent-key-map": "0.2.2",
 		"eslint-import-resolver-node": "0.3.4",
 		"eslint-plugin-eslint-comments": "3.1.2",