Stop processing ScrollTimeline props if no animation-related properties have been declared

[bramus]

While debugging something for #153, I noticed that saveInRelationList was being called once per ruleset – even though only 1 of the processed ruleset in my test had animation-related properties declared.

This PR adds a quick perf win by bailing out early from the handleScrollTimelineProps method in case no animation-related properties have been extracted.

[kevers-google]

Format nit. Let's keep to Google style guidelines.

if (...) {
  return;
}

space after if and statement on a separate line with {} even though 1 line. I'm sure, that I've violated this elsewhere, but no sense proliferating inconsistencies.