docs: make actions/docker a bit clearer

www/docs/ci/actions.md

@@ -38,6 +38,8 @@ jobs:
         with:
           go-version: '>=1.19.1'
           cache: true
+      # More assembly might be required: Docker logins, GPG, etc. It all depends
+      # on your needs.
       - uses: goreleaser/goreleaser-action@v2
         with:
           # either 'goreleaser' (default) or 'goreleaser-pro'

www/docs/customization/docker.md

@@ -122,6 +122,10 @@ dockers:
     - config.yml
 ```
 
+!!! warning
+    Note that you will have to manually login into the Docker registries you
+    want to push to — GoReleaser does not login by itself.
+
 !!! tip
     Learn more about the [name template engine](/customization/templates/).