Stop processing ScrollTimeline props if no animation-related properti…

…es have been declared (#154)

* Don’t bother extracting data from animation-related properties if there are none declared

* Code formatting

src/scroll-timeline-css-parser.js

@@ -212,6 +212,10 @@ export class StyleParser {
     this.saveSourceSelectorToScrollTimeline(rule);
     this.saveSubjectSelectorToViewTimeline(rule);
 
+    if (!hasAnimationTimeline && !hasAnimationName && !hasAnimation) {
+      return;
+    }
+
     let timelineNames = [];
     let animationNames = [];
     let shouldReplacePart = false;