Add bleeding edge macOS arm download

[capital-G]

See https://supercollider.github.io/downloads

This is somehow representing the actual CI step as well, see e.g. https://github.com/supercollider/supercollider/actions/runs/12806874179, which lacks an arm upload

We should probably

• add a CI step for arm upload to s3
• add a download link for said file on the website

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As reported on https://scsynth.org/t/latest-build-of-sc-on-mac/11067

[dyfer]

Sure, we can add arm build.

BTW semi-related - we should probably remove the :latest win32 build: link from the website, as these don't get uploaded anymore.