Notifies using ntfy

Usage:

      - name: Notify
        uses: https://git.lerch.org/lobo/action-notify-ntfy@v1
        if: always()
        with:
          # Can use ** glob syntax for all files
          files: output/**
          user_pin: ${{ secrets.HSM_USER_PIN }}
          # if specified, public key will be used to upload artifacts to the sigstore server
          public_key: https://lerch.org/server_public_key.pem