Merge pull request #3727 from vector-im/dbkr/warn_when_single_instance_quit

Warn when exiting due to single-instance

electron/src/electron-main.js

@@ -171,6 +171,7 @@ const shouldQuit = electron.app.makeSingleInstance((commandLine, workingDirector
 });
 
 if (shouldQuit) {
+    console.log("Other instance detected: exiting");
     electron.app.quit()
 }