Trigger pageviews on pages loaded from bfcache (#4656)

* trigger pageview on pageshow with event.persisted

* update _tracking.html to do the same

lib/plausible_web/templates/layout/_tracking.html.heex

@@ -32,6 +32,13 @@
       }
 
       plausible('pageview', defaultEventOptions)
+
+      window.addEventListener('pageshow', function(event) {
+        if (event.persisted) {
+          // Page was restored from bfcache - trigger a pageview
+          plausible('pageview', defaultEventOptions);
+        }
+      })
     </script>
   <% end %>
 <% end %>

tracker/src/plausible.js

@@ -231,6 +231,15 @@
     } else {
       page()
     }
+
+    {{#if pageleave}}
+    window.addEventListener('pageshow', function(event) {
+      if (event.persisted) {
+        // Page was restored from bfcache - trigger a pageview
+        page();
+      }
+    })
+    {{/if}}
   {{/unless}}
 
   {{#if (any outbound_links file_downloads tagged_events)}}