docs: add index for new symbols in 1.12
diff --git a/docs/libs/gstreamer-libs-docs.sgml b/docs/libs/gstreamer-libs-docs.sgml
index 0b94424..c6f5d6e 100644
--- a/docs/libs/gstreamer-libs-docs.sgml
+++ b/docs/libs/gstreamer-libs-docs.sgml
@@ -113,6 +113,14 @@
     <xi:include href="xml/api-index-deprecated.xml"><xi:fallback /></xi:include>
   </index>
   <index>
+    <title>Index of new API in 1.12.1</title>
+    <xi:include href="xml/api-index-1.12.1.xml"><xi:fallback /></xi:include>
+  </index>
+  <index>
+    <title>Index of new API in 1.12</title>
+    <xi:include href="xml/api-index-1.12.xml"><xi:fallback /></xi:include>
+  </index>
+  <index>
     <title>Index of new API in 1.10</title>
     <xi:include href="xml/api-index-1.10.xml"><xi:fallback /></xi:include>
   </index>