ci: add sha labels for Docker tags (#923)

Author: holtgrewe

.github/workflows/docker-build.yml

@@ -43,8 +43,11 @@ jobs:
         with:
           images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
           tags: |
+            type=schedule
             type=ref,event=branch
+            type=ref,event=tag
             type=ref,event=pr
+            type=sha
 
       - name: Write "git describe --tags --dirty" to VERSION
         run: |