setup: check that ssh to github works

[f-hafner]

In our last workshop at the escience center, I noticed a few people having problems with the ssh authentication on github. I think it would be nice to have people check before the workshop that they can actually authenticate with ssh on github. Ie, after the line "“Add SSH key” button." in the setup instructions, add something like this:

Now, we can check that the ssh connection is working:

ssh -T [email protected]