Fix incorrect help text

src/pretix/control/templates/pretixcontrol/events/create_basics.html

@@ -17,7 +17,7 @@
                 <div class="help-block">
                     {% blocktrans trimmed %}
                         This is the address users can buy your tickets at. Should be short, only contain lowercase
-                        letters and numbers, and must be unique among your events. We recommend some kind of
+                        letters, numbers, dots, and dashes, and must be unique among your events. We recommend some kind of
                         abbreviation or a date with less than 10 characters that can be easily remembered, but you
                         can also choose to use a random value.
                     {% endblocktrans %}