I used the updated firebase in Demo (Example page)

[Tanesan]

I just looked at the demo on your site and tried to write some code, but the firebase used in the demo is a very old version and the specifications have changed quite a bit, so it was not helpful. Also, some people on a programming question site (link below) were having trouble because of this difference in versions, so I made a pull request here. I don't think it would be a good idea to merge and not be able to see the demo of the old version, so how about having two demos, one for the new version and one for the old version? Thank you. https://stackoverflow.com/questions/65104461/getting-error-mapping-over-document-data-flutter