Uses passive listeners to improve scrolling performance

[alvaxet]

Hi,

First of all - thank you for the nice library!

It seems like there is a small space for improvement. I've been running a website audit using google devtools/Lighthouse and I've got this kind of recommendation:

This is it (Learn more link from the screenshot above): https://developers.google.com/web/tools/lighthouse/audits/passive-event-listeners?utm_source=lighthouse&utm_medium=devtools

Recommendations
Add the passive flag to all of the event listeners that Lighthouse has identified. In general, add the passive flag to every wheel, mousewheel, touchstart, and touchmove event listener that does not call preventDefault().

There are a few event listeners (touchstart and touchmove) in the slideout that do not have passive: true on them. That's what I fix with this PR. I didn't commit compiled files

Audit results after the fix:

[coveralls]

Coverage remained the same at 69.88% when pulling 2f15ae8 on alvaxet:touch-performance into 6eb8440 on Mango:master.

[inoas]

Why didnt this get merged?