Fix a link to XML-TO-KDL (#49)

Author: lo48576

src/index.md

@@ -404,7 +404,7 @@ KDL that, even if not entirely idiomatic, is still valid and fits into the
 data models of the other two languages:
 
 * [JSON in KDL](https://github.com/kdl-org/kdl/blob/main/JSON-IN-KDL.md)
-* [XML in KDL](https://github.com/kdl-org/kdl/blob/main/JSON-IN-KDL.md)
+* [XML in KDL](https://github.com/kdl-org/kdl/blob/main/XML-IN-KDL.md)
 
 </section>