Add confirm

js/id/ui/confirm.js

@@ -0,0 +1,14 @@
+iD.confirm = function(message) {
+    var modal = iD.modal();
+    modal.select('.modal').classed('modal-alert', true);
+    modal.select('.content')
+        .append('p').attr('class', 'description');
+    modal.select('.content')
+        .append('button')
+        .text('OK')
+        .on('click', function() {
+            modal.remove();
+        });
+
+    return modal;
+};