Missing dependency when running Jekyll

[mwhamgenomics]

After following the setup instructions for the Carpentries workshop template, I ran into Jekyll errors when running make serve:

$ make serve    
[...]
/usr/local/lib/ruby/gems/3.1.0/gems/jekyll-3.9.2/lib/jekyll/commands/serve/servlet.rb:3:in `require': cannot load such file -- webrick (LoadError)
[...]
make: *** [serve] Error 1

This can be worked around with bundle add webrick, but the permanent fix would be to update this repo's Gemfile in line with the template's one - see carpentries/workshop-template#759.

[zkamvar]

Note: This will be fixed once #212 is merged.