Add a next function

[Azzaare]

In similar fashion as JuliaCon.now(), would it possible to have a next() function that provides the next occuring talks.
So the next talks that have not started yet. Or, if there are none a cool message about JuliaCon 2022 :)

[carstenbauer]

Certainly possible, want to make a PR? 😄

(A tomorrow() pendant to today() would also be nice.)

[IanButterworth]

Ah, I just saw this. Hope I didn't spoil your fun @Azzaare with #21

[Azzaare]

Haha, no, #21 is great. I had one ready due to my integration of JuliaCon.jl in my discord bot, but I will with yours once it is merged :)

As for next, it is a bit more tricky, and I won't have a lot of time for a couple of days. If someone implements it before I can, I won't complain :p