Update the image build action to publish the latest image to a tag wi…

…th just the ruby version

We want to have a versioned image, and a latest version of the image available at a tag with just the ruby version.

So for example, if we release version 0.2.0 of the image for ruby 3.3.0, we will update two tags:

ghcr.io/rails/devcontainer/images/ruby:0.2.0-3.3.0
ghcr.io/rails/devcontainer/images/ruby:3.3.0

.github/workflows/build-and-publish-images.yaml

@@ -49,6 +49,8 @@ jobs:
         with:
           imageName: ghcr.io/rails/devcontainer/images/ruby
           cacheFrom: ghcr.io/rails/devcontainer/images/ruby
-          imageTag: 0.1.0-${{ matrix.RUBY_VERSION }}
+          imageTag:
+            - 0.1.0-${{ matrix.RUBY_VERSION }}
+            - ${{ matrix.RUBY_VERSION }} ]
           subFolder: images/ruby
           push: always