fix(mock-doc): add missing methods to the element mock (#3480)

add the following method stubs to `MockElement`:
- animate
- requestFullscreen
- scrollBy
- scrollTo
- scrollIntoView

all functions accept zero arguments and return nothing (`undefined`).
if in the future that premise needs to be revisited, the team will update
the function signatures at their discretion

src/mock-doc/node.ts

@@ -715,6 +715,9 @@ export class MockElement extends MockNode {
     this.setAttributeNS(null, 'title', value);
   }
 
+  animate() {
+    /**/
+  }
   onanimationstart() {
     /**/
   }
@@ -979,6 +982,18 @@ export class MockElement extends MockNode {
   onwheel() {
     /**/
   }
+  requestFullscreen() {
+    /**/
+  }
+  scrollBy() {
+    /**/
+  }
+  scrollTo() {
+    /**/
+  }
+  scrollIntoView() {
+    /**/
+  }
 
   override toString(opts?: SerializeNodeToHtmlOptions) {
     return serializeNodeToHtml(this as any, opts);