Add needed logger dependency

To avoid this new issue with fresh `bundle install` operations:

  ~/.gem/ruby/default/gems/jekyll-4.4.1/lib/jekyll.rb:26: warning: logger used to be loaded from the standard library, but is not part of the default gems since Ruby 4.0.0.
  You can add logger to your Gemfile or gemspec to fix this error.
  bundler: failed to load command: jekyll (~/.gem/ruby/default/bin/jekyll)
  /opt/homebrew/Cellar/ruby/4.0.1/lib/ruby/4.0.0/bundled_gems.rb:60:in 'Kernel.require': cannot load such file -- logger (LoadError)
    from /opt/homebrew/Cellar/ruby/4.0.1/lib/ruby/4.0.0/bundled_gems.rb:60:in 'block (2 levels) in Kernel#replace_require'
    from ~/.gem/ruby/default/gems/jekyll-4.4.1/lib/jekyll.rb:26:in '<top (required)>'

Author: ctrueden

Gemfile

@@ -20,6 +20,7 @@ gem 'jekyll', '~> 4.2'
 gem 'wdm', '>= 0.1.0' if Gem.win_platform?
 gem 'html-proofer'
 gem 'webrick'
+gem 'logger'
 
 group :jekyll_plugins do
   gem 'jekyll-sitemap'