Add very basic Logger implementation

cpp/Logger.cpp

@@ -0,0 +1,6 @@
+#include "Logger.h"
+#include <iostream>
+
+void Logger::debug(const String &text) {
+    std::cout << "Debug: " << text << std::endl;
+}

include/Logger.h

@@ -0,0 +1,5 @@
+#include "String.h"
+
+class Logger {
+    static void debug(const String &text);
+};