Reposition popover on scroll

src/highlight.ts

@@ -30,6 +30,7 @@ export function refreshActiveHighlight() {
 
   trackActiveElement(activeHighlight);
   refreshStage();
+  repositionPopover(activeHighlight);
 }
 
 function transferHighlight(from: Element, to: Element) {

src/stage.ts

@@ -89,6 +89,7 @@ function mountStage(stagePosition: StageDefinition) {
 }
 
 function renderStage(stagePosition: StageDefinition) {
+  // TODO: cancel rendering if element is not visible
   if (!stageSvg) {
     mountStage(stagePosition);