callbacks

Implement events. For example: "User just logged"

Should be implemented in some way like:

duix.event('USER_JUST_LOGGED'); // not sure if `duix.event` or `duix.dispatch`

duix.listen(‘USER_JUST_LOGGED’, callback);

When racing promises, it can sometimes be useful to know which promise won. Currently, Promise.Race and Promise.First return a promise of the same type as the inputs, and there is no easy way to know which promise won.

I propose adding Promise.RaceWithIndex and Promise.FirstWithIndex that will return Promise<int> for void promises, or Promise<(int winIndex, T result)> for result pro