Explicitly add some gems that we need

While running "bundle exec jekyll serve" there are a bunch of
warnings with the Ruby 3.3:

 logger was loaded from the standard library, but will no longer be part
 of the default gems starting from Ruby 3.5.0.
 You can add logger to your Gemfile or gemspec to silence this warning.
 csv was loaded from the standard library, but will no longer be part of
 the default gems starting from Ruby 3.4.0.
 You can add csv to your Gemfile or gemspec to silence this warning.
 /usr/share/ruby/json/common.rb:3: warning: ostruct was loaded from the
 standard library, but will no longer be part of the default gems starting
 from Ruby 3.5.0.
 You can add ostruct to your Gemfile or gemspec to silence this warning.
 .../vendor/ruby/3.3.0/gems/safe_yaml-1.0.5/lib/safe_yaml/load.rb:22:
 warning: base64 was loaded from the standard library, but will no longer
 be part of the default gems starting from Ruby 3.4.0.
 You can add base64 to your Gemfile or gemspec to silence this warning.

Add the gems to our Gemfile to silence the warnings.

Signed-off-by: Thomas Huth <[email protected]>

Gemfile

@@ -26,3 +26,8 @@ end
 gem "sassc", ">= 2.4.0"
 
 gem "webrick", "~> 1.7"
+
+gem "base64"
+gem "csv"
+gem "logger"
+gem "ostruct"