Fix copying signature files to release assets (#18)

Author: alcaeus

gpg-sign/action.yml

@@ -25,4 +25,4 @@ runs:
  - name: "Move the signature files to the release directory"
  shell: bash
  run: |
- mv ${{inputs.filenames}}.sig $RELEASE_ASSETS
+ for filename in ${{ inputs.filenames }}; do mv ${filename}.sig $RELEASE_ASSETS; done