More work on signal: the C++ part is working

examples/cpptest/main.cpp

@@ -0,0 +1,13 @@
+#include "hello.h"
+#include <iostream>
+
+int main() {
+    static Hello component;
+
+    component._foobar.set_handler([](auto...){
+        std::cout << "Hello from C++" << std::endl;
+    });
+
+    sixtyfps::run(&component);
+
+}