LibXML: Record source location for nodes

Author: https://github.com/DanShaders
Commit: 6368e6ca12
Pull-request: https://github.com/SerenityOS/serenity/pull/20629

Userland/Libraries/LibXML/DOM/Node.h

@@ -19,6 +19,12 @@ struct Attribute {
     DeprecatedString value;
 };
 
+struct Offset {
+    size_t offset { 0 };
+    size_t line { 0 };
+    size_t column { 0 };
+};
+
 struct Node {
     struct Text {
         StringBuilder builder;
@@ -34,6 +40,7 @@ struct Node {
 
     bool operator==(Node const&) const;
 
+    Offset offset;
     Variant<Text, Comment, Element> content;
     Node* parent { nullptr };