Add initial PackIt config

[davide125]

This adds an initial config so we'll get per-commit and per-PR package builds published at https://copr.fedorainfracloud.org/coprs/g/asahi/packit-builds/ which should make testing easier and provide useful signal in case of regressions.

[davide125]

@marcan note that this won't do anything until PackIt is setup for the AsahiLinux org. To do that, follow https://packit.dev/docs/guide/

If this goes well I plan to add it for the other projects we have packaged in Fedora.

[lachmanfrantisek]

@davide125 Hello Davide!

Just randomly got to this PR -- if there's anything missing from Packit's side or you need any help, let us/me know!

[marcan]

I think I can just merge this right? Anything else to do on the side of this repo?

[davide125]

We can merge it but it won't do anything useful until the AsahiLinux github org is onboarded on PackIt. To do that follow the instructions on https://packit.dev/docs/guide/#1-set-up-packit-integration (it basically amounts to installing a github app and then waiting for the ticket to be approved on the packit side).