Show startup errors in a desktop notification

This should make it much easier to spot what goes wrong if you're new to
yabridge and don't know where to look yet.

src/plugin/vst2-plugin.cpp

@@ -53,6 +53,10 @@ extern "C" VST_EXPORT AEffect* VSTPluginMain(
         logger.log("Error during initialization:");
         logger.log(error.what());
 
+        // Also show a desktop notification most people likely won't see the
+        // above message
+        send_notification("Failed to initialize VST2 plugin", error.what());
+
         return nullptr;
     }
 }

src/plugin/vst3-plugin.cpp

@@ -55,6 +55,10 @@ bool InitModule() {
         logger.log("Error during initialization:");
         logger.log(error.what());
 
+        // Also show a desktop notification most people likely won't see the
+        // above message
+        send_notification("Failed to initialize VST3 plugin", error.what());
+
         return false;
     }
 }