As Microsoft plans to shut down Wunderlist and there is no Microsoft To-Do app for MacOS yet, I've created one using nativefier.
I used the following command:
$ nativefier --name "To-Do" -p "OSX" --counter -i ./To-Do --single-instance --width=880 --height=630 --min-width=600 --min-height=330 --internal-urls=false --disable-context-menu https://todo.microsoft.com/login
- Context menu
- Native notifications w/ counter