Docs: Add 'as, match statement' to the index (#99001)

diff --git a/Doc/reference/compound_stmts.rst b/Doc/reference/compound_stmts.rst
index c3c7811..9e09515 100644
--- a/Doc/reference/compound_stmts.rst
+++ b/Doc/reference/compound_stmts.rst
@@ -593,6 +593,7 @@
    keyword: if
    keyword: as
    pair: match; case
+   single: as; match statement
    single: : (colon); compound statement
 
 .. versionadded:: 3.10