fix partial

Author: zkat

src/index.md

@@ -13,5 +13,5 @@ title: The KDL Document Language
 {% include partials/implementations.md %}
 {% include partials/design-and-discussion.md %}
 {% include partials/design-principles.md %}
-{% include partials/compatibility-with-json-and-xml %}
+{% include partials/compatibility-with-json-and-xml.md %}
 {% include partials/faq.md %}