ESLint one-var, no-var rules (#3239)

* fixed issues for eslint one-var and no-var rules

Co-authored-by: Joshi <simplyrender@gmail.com>
Co-authored-by: Andrew Henry <akhenry@gmail.com>

src/plugins/notebook/components/notebook-entry.vue

@@ -249,7 +249,7 @@ export default {
         selectTextInsideElement(element) {
             const range = document.createRange();
             range.selectNodeContents(element);
-            var selection = window.getSelection();
+            let selection = window.getSelection();
             selection.removeAllRanges();
             selection.addRange(range);
         },