GitHub workflow: use scoop instead of chocolatey
GitHub workflow: use scoop instead of chocolatey

Chocolatey requires extra effort to make ImageMagick accessible from
the PATH (https://superuser.com/questions/1571115/how-to-get-the-install-path-of-imagemagick-using-chocolately-on-github-actions-c).

brechtm/rinohtype,brechtm/rinohtype,brechtm/rinohtype