Test gem-based installation

[peterdesmet]

See https://jekyllrb.com/docs/themes/#understanding-gem-based-themes. Default README for this was:

Add this line to your Jekyll site's Gemfile:

gem "petridish"

And add this line to your Jekyll site's _config.yml:

theme: petridish

And then execute:

$ bundle

Or install it yourself as:

$ gem install petridish

[peterdesmet]

This can only work if I publish the gem:

bundle install
gem build petridish.gemspec
gem push petridish-0.2.0.gem

See also this thread