Merge pull request #31 from zipper/fix-responsive-default-expanded

fix: Fixed data attibute name for responsive default expanded items

src/CollapsableItem.ts

@@ -248,7 +248,7 @@ export class CollapsableItem {
 
 	public get isDefaultExpanded(): boolean {
 		const defaultExpandedClass = this.element.classList.contains(this.collapsable.options.classNames.defaultExpanded)
-		const mediaDataset = this.element.dataset.defaultCollapsableExpandedMedia
+		const mediaDataset = this.element.dataset.collapsableDefaultExpandedMedia
 
 		if (defaultExpandedClass || !mediaDataset) {
 			return defaultExpandedClass