LibWeb: Escape text nodes in innerHTML getter

Author: https://github.com/linusg
Commit: https://github.com/SerenityOS/serenity/commit/3436317c083
Pull-request: https://github.com/SerenityOS/serenity/pull/4442
Reviewed-by: https://github.com/awesomekling

Libraries/LibWeb/DOM/Element.cpp

@@ -316,8 +316,10 @@ String Element::inner_html() const
                 builder.append('>');
             }
             if (child->is_text()) {
-                builder.append(downcast<Text>(*child).data());
+                auto& text = downcast<Text>(*child);
+                builder.append(escape_string(text.data(), false));
             }
+            // FIXME: Also handle Comment, ProcessingInstruction, DocumentType
         }
     };
     recurse(*this);