Use @neilsustc/markdown-it-katex instead of markdown-it-katex.
The latter is broken
--@module err
local err={}
function err.file_pos(f, pos, e)
error(string.format("%s:%d: %s", f, pos, e))
end
function err.file(f, e)
error(string.format("%s %s", f, e))
end
return err