LibWebView: Escape HTML within attribute values in the Inspector HTML

If an attribute value contains HTML, let's make sure we render it as
text, instead of injecting HTML in the middle of an Inspector field.

Userland/Libraries/LibWebView/InspectorClient.cpp

@@ -542,7 +542,7 @@ String InspectorClient::generate_dom_tree(JsonObject const& dom_tree)
                 builder.appendff("<span data-node-type=\"attribute\" data-tag=\"{}\" data-attribute-index={} class=\"editable\">", tag, dom_node_attributes.size());
                 builder.appendff("<span class=\"attribute-name\">{}</span>", name);
                 builder.append('=');
-                builder.appendff("<span class=\"attribute-value\">\"{}\"</span>", value_string);
+                builder.appendff("<span class=\"attribute-value\">\"{}\"</span>", escape_html_entities(value_string));
                 builder.append("</span>"sv);
 
                 dom_node_attributes.empend(MUST(String::from_byte_string(name)), MUST(String::from_byte_string(value_string)));