[esp/bindings_js] prevent arrow keys from scrolling

[msbaines]

We are using arrow keys lookUp and lookDown.

Motivation and Context

How Has This Been Tested

Types of changes

• Docs change / refactoring / dependency upgrade
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have completed my CLA (see CONTRIBUTING)
• I have added tests to cover my changes.
• All new and existing tests passed.

[apsdehal]

I am wondering if this is the right way of doing this. Ideally, we shouldn't hack browser defaults. Once the user clicks on the demo and signals that he is ready to immerse into the experience then only we should enable the key bindings. But for now, looks good to go.