docs: add missing 21.10 rlsnotes

This patch extract the release notes that
went into v21.10 & v21.10.1 but that are
missing in master, due to the documentation
refactoring

Type: docs

Change-Id: Icb3c95c71e8cdc255f735990d19ee835e3ce6c6c
Signed-off-by: Nathan Skrzypczak <nathan.skrzypczak@gmail.com>
diff --git a/docs/aboutvpp/releasenotes/index.rst b/docs/aboutvpp/releasenotes/index.rst
index 694096f..1c1732b 100644
--- a/docs/aboutvpp/releasenotes/index.rst
+++ b/docs/aboutvpp/releasenotes/index.rst
@@ -6,6 +6,7 @@
 .. toctree::
     :maxdepth: 2
 
+    v21.10.1
     v21.10
     v21.06
     past