Upgrade jekyll and Ruby

When switching to a new mac, my version of Ruby got bumped up to 3.0 and jekyll to 4.2.0. A few things changed along the way and broke this website. So here is what I had to do to fix it:

• In the _config.yml file, replace gems with plugins. See here
• To install packages, you don’t need to do gem install <package>. You can instead add it to a Gemfile which looks like something like this:

source "https://rubygems.org"

gem "webrick", "~> 1.7"

gem "kramdown-parser-gfm", "~> 1.1"

gem "jekyll-watch", "~> 2.2"

gem "jekyll-paginate"
gem "jekyll-seo-tag"
gem "jekyll-sitemap"
gem "jekyll-gist"

You then run bundle install (you obviously need to install bundle before).

• I had some version conflicts in my dependencies. This was resolved by resorting to bundle again. Instead of doing jekyll serve, you can do:

bundle exec jekyll serve