Fix .eslintrc to resolve react-redux

react-on-rails no longer depends on react-redux.
The template file that uses react-redux should be passed ESLint
regardless its dependency.

.eslintrc

@@ -18,3 +18,7 @@ rules:
 
   # https://github.com/benmosher/eslint-plugin-import/issues/340
   import/no-extraneous-dependencies: 0
+
+settings:
+  import/core-modules:
+    - react-redux