Also include arc4 in the toctree in test vectors
diff --git a/docs/development/test-vectors.rst b/docs/development/test-vectors.rst
index 98e8d51..2f49047 100644
--- a/docs/development/test-vectors.rst
+++ b/docs/development/test-vectors.rst
@@ -387,6 +387,7 @@
 .. toctree::
     :maxdepth: 1
 
+    custom-vectors/arc4
     custom-vectors/cast5
     custom-vectors/idea
     custom-vectors/seed