Update mimetype for Typst source files
According to feedback from project owners Typst uses text/vnd.typst
to be consistent with RFC 6838 section 3.2.
See https://github.com/ubuntu/yaru/issues/4180#issuecomment-2536301213
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According to feedback from project owners Typst uses text/vnd.typst
to be consistent with RFC 6838 section 3.2.
See https://github.com/ubuntu/yaru/issues/4180#issuecomment-2536301213