feat: add Packit integration

Add a basic configuration for building PRs using Packit, using EL 8/9
and supported Fedora's.

The actions are needed to do the "make srpm" way manually, which is
what Copr does.

Signed-off-by: Pino Toscano <[email protected]>

.packit.yaml

@@ -0,0 +1,29 @@
+upstream_package_name: yggdrasil
+downstream_package_name: yggdrasil
+specfile_path: out/yggdrasil.spec
+
+srpm_build_deps:
+  - dnf
+  - gawk
+  - make
+
+actions:
+  post-upstream-clone:
+    - mkdir out
+    - env outdir=out make -f .copr/Makefile srpm
+  get-current-version:
+    - awk '/^Version:/ {print $2;}' out/yggdrasil.spec
+  create-archive:
+    - bash -c 'echo out/yggdrasil-*.tar.*'
+  fix-spec-file:
+    - echo 'nothing to fix'
+
+jobs:
+  - job: copr_build
+    trigger: pull_request
+    targets:
+      - centos-stream-8
+      - centos-stream-9
+      - fedora-all
+      - rhel-8
+      - rhel-9