updated singlefile-core link

WebContent/ui/scripts/bg/missingcore.js

@@ -1,3 +1,3 @@
 if (navigator.vendor.indexOf("Opera") != -1) {
-	document.getElementById("singlefile-core-link").href = "https://addons.opera.com/en/search/?query=singlefile+core";
+	document.getElementById("singlefile-core-link").href = "https://addons.opera.com/fr/extensions/details/singlefile-core";
 }