Document how to recover from lost activation code

weblate/html/registration/registration_complete.html

@@ -7,4 +7,6 @@
 <p>{% blocktrans %}Thank you for registering. You will very soon receive an email with 
 a confirmation link. Please follow this link in order to complete your registration.{% endblocktrans %}</p>
 
+<p>{% blocktrans %}If you don't receive it shortly, please check your spam folder. If it's not there, please <a href="/contact/?subject=Lost activation code">contact us</a>.{% endblocktrans %}</p>
+
 {% endblock %}