feat: implement CPP09 C++20 card

src/task02/main.cpp

@@ -0,0 +1,4 @@
+#include <iostream>
+struct Guard { Guard() { std::cout << "acquire\n"; } ~Guard() { std::cout << "release\n"; } };
+void work(bool short_path) { Guard guard; if (short_path) { std::cout << "work=short\n"; return; } std::cout << "work=long\n"; }
+int main() { work(true); std::cout << "after\n"; }