Bug: No automated build for Apple Silicone

[minthemiddle]

The Github action only builds for x64 for Mac, not for Silicone.

[minthemiddle]

For v1.3 I actually faced the problem that Mac x64 (aka Countdown_1.3.0_x64.dmg) was not built, but Silicone was (Countdown_1.3.0_aarch64.dmg) via main.yml.

I built x64 locally and attached manually for this release.