ci: add latest tag to main branch docker builds

Author: SamyDjemai

.github/workflows/docker-build.yml

@@ -44,6 +44,7 @@ jobs:
         with:
           images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
           tags: |
+            type=raw,value=latest,enable={{is_default_branch}}
             type=ref,event=branch
             type=ref,event=tag
             type=ref,event=pr
@@ -113,6 +114,7 @@ jobs:
         with:
           images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
           tags: |
+            type=raw,value=latest,enable={{is_default_branch}}
             type=ref,event=branch
             type=ref,event=tag
             type=ref,event=pr