Provide architecture diagram #600

Inspired by Image Builder.

Let's provide a simplified architecture diagram that shows which git projects are used.

All our projects should be included:

• packit
• packit-service
• deployment (?)
• ogr
• specfile
• tokman
• *-fedmsg
• copr
• ?

We could also link to external dependencies such as celery, pygithub, python-gitlab, flask?

Image Builder links to commit hashes that are in production: do we want this as well?

TODO:

• Draw that diagram or ask ochosi for contact in UXD that draw theirs
• Discuss about the links if it's enough to just link to the projects