Update documentation with how to setup pages

[CeleritasCelery]

Thanks for the great product! I was following the github instructions on https://feed-me-up-scotty.vincenttunru.com/docs/automate but I couldn't get the results to show up at https://<username>.github.io/feeds/<feedname>.xml. After doing a lot of digging, I realized I had to go to Settings, Pages, and then set the Source to be the gh-pages branch. Otherwise it would not work. I think it would be valuable to update the documentation.

[Vinnl]

Thanks @CeleritasCelery! I was under the impression that that was the default publishing source, but I've updated the readme and project site to explicitly mention this as something to check, so hopefully others won't struggle with this in the future. Let me know if you have further suggestions/requests!