added passive listener indication to event handlers, to resolve perfo… #288
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Added passive event listener indication so browsers supporting this feature will run faster and smoother.
This addresses these types of warnings seen in Dev Tools (Lighthouse):
[Violation] Added non-passive event listener to a scroll-blocking 'touchstart' event. Consider marking event handler as 'passive' to make the page more responsive. See https://www.chromestatus.com/feature/5745543795965952
Using this extra parameter requires feature detection. Instead of adding a third-party feature detection library, embedded feature detection code in a new util module.
Based on: