Add a message to Drupal 8 Log system

Examples:

        \Drupal::logger("mymodule")->alert("Message");
        \Drupal::logger("mymodule")->critical("Message");
        \Drupal::logger("mymodule")->debug("Message");
        \Drupal::logger("mymodule")->emergency("Message");
        \Drupal::logger("mymodule")->error("Message");
        \Drupal::logger("mymodule")->info("Message");
        \Drupal::logger("mymodule")->notice("Message");
        \Drupal::logger("mymodule")->warning("Message");