LibWeb: Allow non-HTMLInputElements to have did_edit_text_node() called

HTMLTextAreaElement also needs to be told when its contained text node
has been edited, so let's make this functionality work for anyone who
extends the new EditableTextNodeOwner interface class.

Userland/Libraries/LibWeb/HTML/HTMLInputElement.h

@@ -7,6 +7,7 @@
 
 #pragma once
 
+#include <LibWeb/DOM/Text.h>
 #include <LibWeb/FileAPI/FileList.h>
 #include <LibWeb/HTML/FormAssociatedElement.h>
 #include <LibWeb/HTML/HTMLElement.h>
@@ -41,7 +42,8 @@ namespace Web::HTML {
 
 class HTMLInputElement final
     : public HTMLElement
-    , public FormAssociatedElement {
+    , public FormAssociatedElement
+    , public DOM::EditableTextNodeOwner {
     WEB_PLATFORM_OBJECT(HTMLInputElement, HTMLElement);
     FORM_ASSOCIATED_ELEMENT(HTMLElement, HTMLInputElement)
 
@@ -83,8 +85,6 @@ public:
 
     bool is_mutable() const { return m_is_mutable; }
 
-    void did_edit_text_node(Badge<BrowsingContext>);
-
     JS::GCPtr<FileAPI::FileList> files();
     void set_files(JS::GCPtr<FileAPI::FileList>);
 
@@ -101,6 +101,9 @@ public:
 
     WebIDL::ExceptionOr<void> show_picker();
 
+    // ^DOM::EditableTextNodeOwner
+    virtual void did_edit_text_node(Badge<BrowsingContext>) override;
+
     // ^EventTarget
     // https://html.spec.whatwg.org/multipage/interaction.html#the-tabindex-attribute:the-input-element
     virtual bool is_focusable() const override { return m_type != TypeAttributeState::Hidden; }