Document what users of Fedora automation needs to be aware of

[lachmanfrantisek]

Let's create a page covering all the information, warnings and concerns people might need to think about when enabling Packit for their package.

This doc page can then be linked from onboarding PRs (packit/packit-service#2506) or when creating new releases. (Still, a bit of text might need to be added since people might ignore the link.)

A list of things to be included:

• The maintainer is responsible for reviews and caring about the package state.
• Be careful about dependent packages. (Not watched by CI.)
• Be careful about spam for co-maintainers (e.g. EPEL SIG) when not caring about Packit-produced PRs.
• Know how to retrigger or fix issues locally.
• Be aware of the specifics of the package ecosystems.

Please, suggest more things worth covering...

[lbarcziova]

This should be probably placed under https://packit.dev/docs/fedora-releases-guide and could be also linked from the FAQ.