examples enhance

* utils for products generator

* load test for each *.test.js file in packages folder

* [test] unit test for utils/common

* refactor all products with productGenerator for all examples

* refactor folder structure

* move component <Code /> to src/components/common
* rename component file name

package.json

@@ -70,7 +70,7 @@
     ],
     "testEnvironment": "node",
     "testMatch": [
-      "**/test/*.js"
+      "**/test/**/*.js"
     ]
   }
 }