Correctly lowercase the image name.

Author: brycelelbach

.github/workflows/build-docker-image.yml

@@ -21,11 +21,14 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v4
 
-      - name: Docker metadata
+      - name: Set image name
+        run: echo "IMAGE=ghcr.io/${GITHUB_REPOSITORY,,}" >> $GITHUB_ENV
+
+      - name: Set Docker metadata
         id: meta
         uses: docker/metadata-action@v5
         with:
-          images: ghcr.io/${{ toLower(github.repository) }}
+          images: ${{ env.IMAGE }}
           tags: |
             type=raw,value=latest,enable={{is_default_branch}}
             type=sha