Add logging function to C++ builder

src/lib-cpp/include/Velopack.hpp

@@ -229,6 +229,14 @@ public:
         return VelopackApp(); 
     };
 
+    /**
+     * Attach a custom callback to receive log messages from Velopack.
+     */
+    VelopackApp& SetLogger(vpkc_log_callback_t cbInstall, void* p_user_data) {
+        vpkc_set_logger(cbInstall, p_user_data);
+        return *this;
+    };
+
     /**
      * Set whether to automatically apply downloaded updates on startup. This is ON by default.
      */