de-lint email, extend

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

src/extend.js

@@ -17,7 +17,7 @@ limitations under the License.
 'use strict';
 
 module.exports = function(dest, src) {
-    for (var i in src) {
+    for (const i in src) {
         if (src.hasOwnProperty(i)) {
             dest[i] = src[i];
         }