close-merge input

Fixes: https://code.forgejo.org/actions/cascading-pr/issues/7

action.yml

@@ -60,6 +60,9 @@ inputs:
     required: true
   prefix:
     description: 'prefix of the cascading PR created on destination-repo (default to {origin-repo})'
+  close-merge:
+    description: 'if true the cascading PR will be closed and the branch deleted when the PR is merged'
+    default: false
   verbose:
     description: 'if true print verbose information'
     default: false
@@ -97,4 +100,5 @@ runs:
                         --destination-branch "${{ inputs.destination-branch }}" \
                         --update "${{ inputs.update }}" \
                         --prefix "${{ inputs.prefix }}" \
+                        --close-merge "${{ inputs.close-merge }}" \
                         run