handle "data-original" attribute while processing lazy loaded images

lib/single-file/single-file-core.js

@@ -286,6 +286,12 @@ const SingleFileCore = (() => {
 					imgElement.removeAttribute("data-src");
 				}
 			});
+			this.doc.querySelectorAll("img[data-original]").forEach(imgElement => {
+				if (imgElement.dataset.original && imgElement.src != imgElement.dataset.original) {
+					imgElement.src = imgElement.dataset.original;
+					imgElement.removeAttribute("data-original");
+				}
+			});
 			this.doc.querySelectorAll("[data-bg]").forEach(element => {
 				if (element.dataset.bg && !element.style.backgroundImage.includes(element.dataset.bg)) {
 					element.style.backgroundImage = "url(" + element.dataset.bg + ")";