deprecated workflow

[typemytype]

Warning: The set-output command is deprecated and will be disabled soon. Please upgrade to using Environment Files. For more information see: https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/

https://github.com/typemytype/drawbot/actions/runs/3750328273/jobs/6369899166#step:12:10

[justvanrossum]

Ah, they've improved the documentation for this a lot.

Earlier, I couldn't do it without this: https://hynek.me/til/set-output-deprecation-github-actions/