Add event selection explanation to welcome email type

assets/js/src/newsletters/types/welcome.jsx

@@ -155,6 +155,8 @@ define(
             <h1>{MailPoetI18n.welcomeEmail}</h1>
             <Breadcrumb step="type" />
 
+            <h3>{MailPoetI18n.selectEventToSendWelcomeEmail}</h3>
+
             <Select
               field={events}
               item={this.state}

views/newsletters.html

@@ -49,6 +49,7 @@
     'nth': __('%$1dth'),
     'next': __('Next'),
 
+    'selectEventToSendWelcomeEmail': __('Select an event to send this welcome email'),
     'whenSomeoneSubscribesToList': __('When someone subscribes to the list...'),
     'whenWordpressUserIsAdded': __('When a new Wordrpess user is added to your site...'),
     'delayImmediately': __('immediately.'),