add timeout before copying password

src/popup/pwgen.js

@@ -35,11 +35,15 @@ function saveOptions(options) {
 }
 
 function copypasstoclippboard() {
+  setTimeout(function() {
     var copyText = document.getElementById('pw');
     copyText.select();
     document.execCommand('copy');
+  }, 100);
 }
 
+document.addEventListener('DOMContentLoaded', function() {
+
   document.getElementById('new').addEventListener('click', (ev) => {
     ev.preventDefault();
     var params = getParams();
@@ -68,3 +72,6 @@ loadOptions().then((options) => {
       copypasstoclippboard();
     }
   });
+
+});
+