fix: support Ruby 4.0 and upgrade Re:VIEW to 5.11.0

- Re:VIEW 5.3.0 -> 5.11.0 for Ruby 4.0 compatibility
- Add nkf gem (removed from Ruby stdlib in 3.4)
- Add permitted_classes: [Date] to YAML.load_file for Psych security

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: piti6

Gemfile

@@ -1,7 +1,8 @@
 # A sample Gemfile
 source "https://rubygems.org"
 
-gem 'review', '5.3.0'
+gem 'review', '5.11.0'
 gem 'pandoc2review'
 gem 'rake'
+gem 'nkf'
 # gem 'review-peg', '0.2.2'

articles/lib/tasks/z01_pandoc2review.rake

@@ -31,7 +31,7 @@ end
 
 desc 'run pandoc2review'
 task :pandoc2review do
-  config = YAML.load_file(CONFIG_FILE)
+  config = YAML.load_file(CONFIG_FILE, permitted_classes: [Date])
   if config['contentdir'] == '_refiles'
     path = '_refiles'
     p2r = 'pandoc2review'