feat(index): Added flowtype eslint plugin (#20)

Currently sku lint uses the eslint-config-seek as it's eslint config. In projects using eslint and
flow, the configuration would need to be updated for flow utility types (as an example) that will
report an eslint error when used.

index.js

@@ -209,6 +209,6 @@ module.exports = {
     'import/default': 'error',
     'import/export': 'error'
   },
-  plugins: ['react', 'css-modules', 'import'],
-  extends: ['plugin:css-modules/recommended', 'prettier']
+  plugins: ['react', 'css-modules', 'import', 'flowtype'],
+  extends: ['plugin:css-modules/recommended', 'prettier', 'plugin:flowtype/recommended']
 };

package.json

@@ -24,6 +24,7 @@
     "eslint-config-prettier": "^2.3.0",
     "eslint-import-resolver-node": "^0.3.0",
     "eslint-plugin-css-modules": "^2.7.1",
+    "eslint-plugin-flowtype": "^2.46.1",
     "eslint-plugin-import": "^2.2.0",
     "eslint-plugin-react": "^7.0.1",
     "find-root": "^1.1.0"