Using showdown with katex from command line

[bene51]

Hi,

please apologize but I seem to be unable to find how to do this. I installed

npm install showdown -g
npm install showdown-katex -g

Now I wonder how I specify the katex extension. I tried

showdown makehtml -i index.md -e showdown-katex -o index.html -p github

which results in

Could not load extension showdown-katex.

Could somebody please point me in the right direction?

Thx, Bene