Allow wider Jekyll for Ruby 3 support

Author: PeterJCLaw

Gemfile

@@ -6,7 +6,7 @@ gem 'kramdown'
 # jekyll depends on kramdown-parser-gfm, but fails to declare it
 gem 'kramdown-parser-gfm'
 # Pin to the version used on GitHub Pages
-gem 'jekyll', 3.9
+gem 'jekyll', '~> 3'
 gem 'jekyll-redirect-from'
 
 # For testing output

Gemfile.lock

@@ -5,6 +5,7 @@ GEM
       public_suffix (>= 2.0.2, < 7.0)
     colorator (1.1.0)
     concurrent-ruby (1.3.4)
+    csv (3.3.0)
     em-websocket (0.5.3)
       eventmachine (>= 0.12.9)
       http_parser.rb (~> 0)
@@ -25,13 +26,14 @@ GEM
       yell (~> 2.0)
       zeitwerk (~> 2.5)
     http_parser.rb (0.8.0)
-    i18n (0.9.5)
+    i18n (1.14.5)
       concurrent-ruby (~> 1.0)
-    jekyll (3.9.0)
+    jekyll (3.10.0)
       addressable (~> 2.4)
       colorator (~> 1.0)
+      csv (~> 3.0)
       em-websocket (~> 0.5)
-      i18n (~> 0.7)
+      i18n (>= 0.7, < 2)
       jekyll-sass-converter (~> 1.0)
       jekyll-watch (~> 2.0)
       kramdown (>= 1.17, < 3)
@@ -40,6 +42,7 @@ GEM
       pathutil (~> 0.9)
       rouge (>= 1.7, < 4)
       safe_yaml (~> 1.0)
+      webrick (>= 1.0)
     jekyll-redirect-from (0.16.0)
       jekyll (>= 3.3, < 5.0)
     jekyll-sass-converter (1.5.2)
@@ -97,7 +100,7 @@ PLATFORMS
 
 DEPENDENCIES
   html-proofer (~> 4)
-  jekyll (= 3.9)
+  jekyll (~> 3)
   jekyll-redirect-from
   kramdown
   kramdown-parser-gfm