Add param to #arrange learn more link for GA. Bug 1020528.

bedrock/firefox/templates/firefox/desktop/tips.html

@@ -144,7 +144,7 @@
               <h4>{{ _('How to:') }}</h4>
               <p>
                 {{ _('Open the menu, select “<strong>Customize</strong>” and drag any button into the toolbar or menu.') }}
-                <a rel="external" href="https://support.mozilla.org/kb/customize-firefox-controls-buttons-and-toolbars">
+                <a rel="external" href="https://support.mozilla.org/kb/customize-firefox-controls-buttons-and-toolbars?src=tips-arrange">
                 {% if l10n_has_tag('sync_device_note') or settings.DEV %}
                   {{ _('Learn more about customizing') }}
                 {% else %}