Improve grunt/.jshintrc
Merge pull request #12760 from ZDroid/grunt-jshintrc

Improve grunt/.jshintrc
Improve `js/tests/index.html`
- Improve comments.
- Remove `transition.js` script load as `transition.js` unit test doesn't exist.
Merge pull request #12772 from ZDroid/tests-index

Improve `js/tests/index.html`