fix(carousel): avoid right click dragging

[nandaleite]

Description

Add MouseEvent.button property inside onStart() function, to identify which button was pressed on the mouse to trigger the event.

Motivation and Context

Right click was triggering drag event.
Issue ➜ Bug: Right click event triggers screen drag event listener #249

How Has This Been Tested?

Tested manually on Firefox 65.0.1, Safari 11.0.3 and Chrome 72.0.3626.119

Screenshots (if appropriate):

Types of changes

• 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 not work as expected)

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 included a vue-play example (if this is a new feature)

[coveralls]

Coverage decreased (-0.4%) to 67.278% when pulling 3fc7b99 on nandaleite:bug-right-click-drag into c793ceb on SSENSE:master.

[quinnlangille]

Hey @nandaleite, sorry for the delay on reviewing. Thanks a million for the PR. This looks like it fixes #249 - great thinking! I'm merging it into our next release candidate now, I'll ping you in the change log when it's released 🚀

[nandaleite]

That's wonderful! Thanks for you reply, @quinnlangille