Add declaration_list to c-ts-common-indent-type-regexp-alist

* lisp/progmodes/c-ts-mode.el (c-ts-base-mode): Consider a
"declaration_list" a block. (Bug#61635)
* test/lisp/progmodes/c-ts-mode-resources/indent.erts (Code): Add a
test case.

lisp/progmodes/c-ts-mode.el

@@ -814,7 +814,8 @@ the semicolon.  This function skips the semicolon."
               `((block . ,(rx (or "compound_statement"
                                   "field_declaration_list"
                                   "enumerator_list"
-                                  "initializer_list")))
+                                  "initializer_list"
+                                  "declaration_list")))
                 (if . "if_statement")
                 (else . ("if_statement" . "alternative"))
                 (do . "do_statement")

test/lisp/progmodes/c-ts-mode-resources/indent.erts

@@ -369,3 +369,19 @@ int main()
   };
 }
 =-=-=
+
+Code:
+  (lambda ()
+    (c++-ts-mode)
+    (setq-local indent-tabs-mode nil)
+    (setq-local c-ts-mode-indent-offset 2)
+    (indent-region (point-min) (point-max)))
+
+Name: Declaration List (Namespace) (Bug#61635)
+
+=-=
+namespace test {
+  class Name {
+  };
+}
+=-=-=