This commit drops Arch Linux in favor of a BSD so there's more variety in CI. Link: https://lists.sr.ht/~rjarry/aerc-devel/%3C20220122033806.91728-1-ktprograms%40gmail.com%3E
Add build and test on debian, fedora and archlinux. Only check code formatting on alpine. Signed-off-by: Robin Jarry <robin@jarry.cc>