Use lowercase in repository name so that tag is valid

Author: Sri Ramanujam

.github/workflows/publish.yml

@@ -29,6 +29,9 @@ jobs:
       -
         name: Set tag name in environment
         run: echo "RELEASE_VERSION=${GITHUB_REF#refs/*/}" >> $GITHUB_ENV
+      -
+        name: Set lowercase repository in environment
+        run: echo "REPOSITORY_LOWERCASE=${GITHUB_REPOSITORY,,}" >> $GITHUB_ENV
       -
         name: Build and push
         uses: docker/build-push-action@v2
@@ -37,5 +40,5 @@ jobs:
           platforms: linux/amd64,linux/arm64
           push: true
           tags: |
-            ghcr.io/${{ github.repository }}:latest
-            ghcr.io/${{ github.repository }}:${{ env.RELEASE_VERSION }}
+            ghcr.io/${{ env.REPOSITORY_LOWERCASE }}:latest
+            ghcr.io/${{ env.REPOSITORY_LOWERCASE }}:${{ env.RELEASE_VERSION }}