Trigger event listener for keys at capturing phase

[apsdehal]

Motivation and Context

Sometimes users have extensions enabled which override default key behavior. This change intends to fix that behavior by triggering the event listener for keys at the capturing phase so it can't be stopped via event.stopPropagation(). See https://stackoverflow.com/questions/13880126/override-existing-onkeydown-function

How Has This Been Tested

Tested on viewer

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.

[msbaines]

Thanks for fixing!