Add a script to create Vagrant Cloud entries

Merge Request Required Information

Summary of Changes

The goal of this script is to create entries on https://app.vagrantup.com/centos for Vagrant boxes.

In https://lists.centos.org/pipermail/centos-devel/2023-March/142841.html it was suggested to upload the script here.

For now this is really an early and untested version. I've verified most of the script, just not the actual API calls.

Another thing is that it doesn't ensure the box actually exists. Today the CentOS Stream 9 box doesn't exist, so that will fail. Is it desired to ensure the version?

I've also used bash since that's what the docs used.

Another thing that can be debated is the retrieval of the checksum over the internet. If this script has access to the real files, it's safer (and probably more reliable) to read those directly.

Approved Bugzilla Ticket

All submissions to CentOS Stream must reference an approved ticket in Red Hat Bugzilla. Please follow the CentOS Stream contribution documentation for how to file this ticket and have it approved.