Feat: Add support for replaying :defined pseudo-class of custom elements (#1155)

* Feat: Add support for replaying :defined pseudo-class of custom elements

* add isCustom flag to serialized elements

Applying Justin's review suggestion

* fix code lint error

* add custom element event

* fix: tests (#1348)

* Update packages/rrweb/src/record/observer.ts

* Update packages/rrweb/src/record/observer.ts

---------

Co-authored-by: Nafees Nehar <nafees87n@gmail.com>
Co-authored-by: Justin Halsall <Juice10@users.noreply.github.com>

packages/rrweb-snapshot/src/rebuild.ts

@@ -142,6 +142,18 @@ function buildNode(
       if (n.isSVG) {
         node = doc.createElementNS('http://www.w3.org/2000/svg', tagName);
       } else {
+        if (
+          // If the tag name is a custom element name
+          n.isCustom &&
+          // If the browser supports custom elements
+          doc.defaultView?.customElements &&
+          // If the custom element hasn't been defined yet
+          !doc.defaultView.customElements.get(n.tagName)
+        )
+          doc.defaultView.customElements.define(
+            n.tagName,
+            class extends doc.defaultView.HTMLElement {},
+          );
         node = doc.createElement(tagName);
       }
       /**