Auto merge of #25576 - pshaughn:menuelement, r=jdm

Implement HTMLMenuElement

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Per spec, "The menu element is simply a semantic alternative to ul to express an unordered list of commands (a "toolbar")." We already have the CSS for it in user-agent.css, and this gives us the interface object.

---
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- [X] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [X] These changes fix #24990

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- [X] There are tests for these changes

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components/script/dom/webidls/HTMLMenuElement.webidl

@@ -0,0 +1,17 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+// https://html.spec.whatwg.org/multipage/#htmlmenuelement
+[Exposed=Window]
+interface HTMLMenuElement : HTMLElement {
+  [HTMLConstructor] constructor();
+
+  // also has obsolete members
+};
+
+// https://html.spec.whatwg.org/multipage/#HTMLMenuElement-partial
+partial interface HTMLMenuElement {
+   [CEReactions]
+            attribute boolean compact;
+};