Fixed feedback widget not mounting with instant navigation (#8275)

Author: staadecker

docs/setup/setting-up-site-analytics.md

@@ -273,25 +273,29 @@ generated by users interacting with the feedback widget with the help of some
 === ":octicons-file-code-16: `docs/javascripts/feedback.js`"
 
     ``` js
-    var feedback = document.forms.feedback
-    feedback.hidden = false // (1)!
-
-    feedback.addEventListener("submit", function(ev) {
-      ev.preventDefault()
-
-      var page = document.location.pathname // (2)!
-      var data = ev.submitter.getAttribute("data-md-value")
-
-      console.log(page, data) // (3)!
-
-      feedback.firstElementChild.disabled = true // (4)!
-
-      var note = feedback.querySelector(
-        ".md-feedback__note [data-md-value='" + data + "']"
-      )
-      if (note)
-        note.hidden = false // (5)!
-    })
+    document$.subscribe(function() {
+      var feedback = document.forms.feedback
+      if (typeof feedback === "undefined") return
+      
+      feedback.hidden = false // (1)!
+  
+      feedback.addEventListener("submit", function(ev) {
+        ev.preventDefault()
+  
+        var page = document.location.pathname // (2)!
+        var data = ev.submitter.getAttribute("data-md-value")
+  
+        console.log(page, data) // (3)!
+  
+        feedback.firstElementChild.disabled = true // (4)!
+  
+        var note = feedback.querySelector(
+          ".md-feedback__note [data-md-value='" + data + "']"
+        )
+        if (note)
+          note.hidden = false // (5)!
+      })
+    }
     ```
 
     1.  The feedback widget is hidden by default so that it does not appear when