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

(cherry picked from commit 26720ff)

Co-authored-by: Hugo van Kemenade <[email protected]>

Author: miss-islington

Doc/reference/compound_stmts.rst

@@ -593,6 +593,7 @@ The :keyword:`!match` statement
    keyword: if
    keyword: as
    pair: match; case
+   single: as; match statement
    single: : (colon); compound statement
 
 .. versionadded:: 3.10