Add Oracle challenge to ethereum.org oracles page

[escottalexander]

Suggested by Azimov, once this challenge is live it would be easy to add it as a link under Tutorials on this page: https://ethereum.org/developers/docs/oracles/

[rin-st]

Hey @escottalexander and @AzimovS ! Could you add the challenge to the tutorials?

[escottalexander]

We can follow it here: ethereum/ethereum-org-website#18176

[escottalexander]

It has been added to the dev branch!

[rin-st]

Great, thank you! Let's wait until it's live and then close the issue