Fix an issue with newer Ruby version, see https://talk.jekyllrb.com/t/load-error-cannot-load-such-file-webrick/5417/14

Gemfile

@@ -1,2 +1,4 @@
 source 'https://rubygems.org'
 gem 'github-pages', group: :jekyll_plugins
+
+gem "webrick", "~> 1.7"

Gemfile.lock

@@ -251,6 +251,7 @@ GEM
       unf_ext
     unf_ext (0.0.8.2)
     unicode-display_width (1.8.0)
+    webrick (1.7.0)
     zeitwerk (2.6.0)
 
 PLATFORMS
@@ -258,6 +259,7 @@ PLATFORMS
 
 DEPENDENCIES
   github-pages
+  webrick (~> 1.7)
 
 BUNDLED WITH
    2.3.5