GH CI: Update runner OS and actions/checkout version
Okay I really need to release a new Vibe.d :)
Needs https://github.com/rejectedsoftware/ddox/pull/233
@Geod24 is this still blocked? Needing a new tag? (https://github.com/rejectedsoftware/ddox/issues/234)
what would we need to update in dub or is dub fetching ddox online?
Need a new tag, but I think I know a workaround...
The workaround (which I was about to remove...) works.
but wait should we actually upgrade the ubuntu version? I think it's best to keep it on the oldest version, so that built executables work on older linux distros as well.
Well 18.04 is deprecated. So we need to upgrade at least to 20.04.
Okay, let's move ahead with this when the CI (except for master) is green.