externals: Add catch2 v3.2.1

Merge commit '6879e5bb1c598a9a517d7bdec8ba1a0bace3ef10' as 'externals/catch'

externals/catch/tests/SelfTest/UsageTests/VariadicMacros.tests.cpp

@@ -0,0 +1,29 @@
+
+//              Copyright Catch2 Authors
+// Distributed under the Boost Software License, Version 1.0.
+//   (See accompanying file LICENSE.txt or copy at
+//        https://www.boost.org/LICENSE_1_0.txt)
+
+// SPDX-License-Identifier: BSL-1.0
+
+#include <catch2/catch_test_macros.hpp>
+
+
+TEST_CASE()
+{
+    SUCCEED( "anonymous test case" );
+}
+
+TEST_CASE( "Test case with one argument" )
+{
+    SUCCEED( "no assertions" );
+}
+
+TEST_CASE( "Variadic macros", "[variadic][sections]" )
+{
+    SECTION( "Section with one argument" )
+    {
+        SUCCEED( "no assertions" );
+    }
+}
+