feat: add comments how to add access token for registry login

.gitea/workflows/publish-docker.yml

@@ -18,9 +18,11 @@ jobs:
         uses: docker/login-action@v3
         with:
           registry: git.br0tkasten.de
-          # Gitea provides these variables automatically
           username: ${{ gitea.actor }}
-          password: ${{ secrets.TOKEN }}
+          # access token of the user triggering this action
+          # in gitea -> user settings -> applications -> new token -> write:packages and write:repositories
+          # then in gitea -> user settings -> actions -> secrets -> add new secret named "TOKEN" with the value of the access token.
+          password: ${{ secrets.TOKEN }} 
 
       - name: Extract metadata (tags, labels) for Docker
         id: meta