Adding a 'beta' cask to homebrew-cask-versions

[eloyaldea]

Hi! After contributing a lot to updating casks in the regular homebrew-cask GitHub page, I want to add a 'beta' version to the cask WhatsApp as it has just been released.
I checked this guide on the homebrew-cask-versions GitHub, which redirects to this other guide from the main homebrew-cask GitHub but after taking the necessary steps to set up the new cask locally, I couldn't find instructions to make the PR into homebrew-cask-versions instead of the default homebrew-cask.
Any help? Thanks!