Retrieve the plaintext representation of a software license by its SPDX identifier.
$ curl https://fetchalicense.com/Apache-2.0 > LICENSE
$ curl https://fetchalicense.com/CC0-1.0 > LICENSE
$ curl https://fetchalicense.com/GPL-3.0-or-later > COPYING
$ curl https://fetchalicense.com/MIT > LICENSE
$ curl https://fetchalicense.com/Unlicense > LICENSE