Fix update readme workflow

[lucasrod16]

The workflow that keeps dockerhub image descriptions in sync with readmes is failing. It would be nice to have this automation working so that dockerhub image descriptions stay updated with changes to source readmes in this repository.

https://github.com/rstudio/rstudio-docker-products/actions/workflows/update-readme.yaml

There are currently two causes of the failures:

1. there are no readmes in the content/base and content/pro directories which causes the peter-evans/dockerhub-description github action to fail with the following errors:

   ENOENT: no such file or directory, open './content/base/README.md'
   ENOENT: no such file or directory, open './content/pro/README.md'
   

   • there is a single readme under content/README.md that documents both the base and pro images

2. the rest of the errors are Forbidden errors. these are likely caused by the dockerhub access token having insufficient permissions

   • the access token used in the password input for the peter-evans/dockerhub-description github action must have read/write/delete scope. https://github.com/peter-evans/dockerhub-description?tab=readme-ov-file#action-inputs

peter-evans/dockerhub-description#10
peter-evans/dockerhub-description#248

[lucasrod16]

Ran a test in a personal repository to verify an access token with read/write/delete permissions is able to successfully update a dockerhub description using the peter-evans/dockerhub-description action:

https://github.com/lucasrod16/update-dockerhub-description-test/actions/runs/13078426464/job/36496180268#step:3:11
https://hub.docker.com/repository/docker/lucasrod96/update-dockerhub-description/general

[emcrisan]

came up in ticket 115766

[ianpittwood]

We determined the permissions errors to be a result of our switch from using a PAT for image management to using an OAT. There is currently a ticket open for the action for OAT support. I was able to progress past the initial authentication issue in a PR, but it seems OATs may lack the proper permissions to update repositories. Unfortunately, the endpoint being hit for repository updates doesn't even appear to be public.