Relax ESLint config peerDependency (facebook#1740)

Author: gaearon

packages/eslint-config-react-app/package.json

@@ -15,7 +15,7 @@
     "eslint": "^3.16.1",
     "eslint-plugin-flowtype": "^2.21.0",
     "eslint-plugin-import": "^2.0.1",
-    "eslint-plugin-jsx-a11y": "^4.0.0",
+    "eslint-plugin-jsx-a11y": "^2.0.0 || ^3.0.0 || ^4.0.0",
     "eslint-plugin-react": "^6.4.1"
   }
 }