typst binary in repo

Due to the regular changes in typst, documents are currently highly dependant on specific compiler versions. Manually downloading/installing a specific typst version is highly annoying so I propose to fix the version for any concrete version/copy of this repo. There are multiple ways to do that:

• Typst's binary/binaries have a reasonable size and could be put into the repo. This way we have a fully self-sufficient document, which is desirable, especially for a thesis that might be archived for many decades to come.
• Instead of storing binaries in the repo, we could just store the version and then download the binary from github, when needed. Binary paths could be put into .gitignore.

For the downloading-from-github part: https://gitlab.gwdg.de/glissmann/setup-typst. It seems quite tricky to download the most recent version of a package from github. We could use this to permanently store the typst version as well.

I'm unsure what the best way is and would welcome insights from @janphilipp.ressler and others ;)