Squashed 'external/entt/entt/' content from commit fef92113

git-subtree-dir: external/entt/entt
git-subtree-split: fef921132cae7588213d0f9bcd2fb9c8ffd8b7fc

test/lib/emitter/lib.cpp

@@ -0,0 +1,8 @@
+#include <entt/core/attribute.h>
+#include "types.h"
+
+ENTT_API void emit(test_emitter &emitter) {
+    emitter.publish(event{});
+    emitter.publish(message{42});
+    emitter.publish(message{3});
+}