Add logger to Gemfile to fix Ruby 3.5.0 deprecation warning

This gem will be moved out of the standard library in Ruby 3.5.0.
While the website can still build fine with Ruby 3.4.x, this won't
be the case anymore with the latest Ruby version once 3.5.0 releases.

Gemfile

@@ -11,3 +11,5 @@ gem 'webrick', '~> 1.8'
 gem 'csv'
 gem 'base64'
 gem 'bigdecimal'
+
+gem "logger", "~> 1.7"

Gemfile.lock

@@ -90,6 +90,7 @@ GEM
     listen (3.9.0)
       rb-fsevent (~> 0.10, >= 0.10.3)
       rb-inotify (~> 0.9, >= 0.9.10)
+    logger (1.7.0)
     mercenary (0.4.0)
     pathutil (0.16.2)
       forwardable-extended (~> 2.6)
@@ -169,6 +170,7 @@ DEPENDENCIES
   jekyll-paginate-v2
   jekyll-redirect-from
   jekyll-watch
+  logger (~> 1.7)
   webrick (~> 1.8)
 
 BUNDLED WITH