LibWeb: Propagate input/textarea selection update to document selection

Calling `.setSelectionRange()` or `.select()` now updates the document
selection as well, visualizing the text selection.

(cherry picked from commit 732e3fa82f216a6f4114eb0e6bb89e167e95ab42)

Userland/Libraries/LibWeb/HTML/HTMLInputElement.h

@@ -197,6 +197,9 @@ public:
     bool select_applies() const;
     bool selection_or_range_applies() const;
 
+protected:
+    void selection_was_changed() override;
+
 private:
     HTMLInputElement(DOM::Document&, DOM::QualifiedName);