This adds a new workflow for building and releasing _tagged versions_
of Ghostty. The workflow is triggered automatically by new tags in the
format of `vX.Y.Z` but can also be manually triggered by running the
workflow from the GitHub Actions UI.
Release artifacts are uploaded to a completely separate R2 bucket
with its own access policy, retention, API keys, and so on.
There is currently no way to switch between "channels" in the macOS
app. I will follow up with a separate commit to add this feature.
Fixes#2673
Rather than document this too much, I think it makes sense to just
default this to true when system package mode is enabled (`--system`)
since it seems that in multiple package ecosystems this is the desired
behavior.
This can still be overridden by setting `-Dpie=false`.
