externals: Add catch2 v3.2.1

Merge commit '6879e5bb1c' as 'externals/catch'

externals/catch/tests/ExtraTests/X90-WindowsHeaderInclusion.cpp

@@ -0,0 +1,21 @@
+
+//              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
+
+/**\file
+ * Test that the Catch2 header compiles even after including windows.h
+ * without defining NOMINMAX first.
+ *
+ * As an FYI, if you do that, you are wrong.
+ */
+
+#include <windows.h>
+#include <catch2/catch_test_macros.hpp>
+
+TEST_CASE("Catch2 did survive compilation with windows.h", "[compile-test]") {
+    SUCCEED();
+}