chore: import upstream snapshot with attribution

examples/cpp/stdio/main.cpp

@@ -0,0 +1,17 @@
+#include <iostream>
+#include <string>
+
+#include <rerun.hpp>
+
+int main() {
+    const auto rec = rerun::RecordingStream("rerun_example_stdio");
+    rec.to_stdout().exit_on_failure();
+
+    std::string input;
+    std::string line;
+    while (std::getline(std::cin, line)) {
+        input += line + '\n';
+    }
+
+    rec.log("stdin", rerun::TextDocument(input));
+}