Extract a docker tag when CI is triggered by a pull request

Author: Sparrow0hawk

.github/workflows/ci.yml

@@ -82,6 +82,7 @@ jobs:
         tags: |
           type=semver,pattern={{version}}
           type=ref,event=branch,enable={{is_not_default_branch}}
+          type=ref,event=pr,enable={{is_not_default_branch}}
           type=raw,value=latest,enable={{is_default_branch}}
 
     - name: Build and push image