Merge pull request #1823 from progit/dependabot/bundler/epubcheck-ruby-5.0.0.0

Update epubcheck-ruby requirement from 4.2.6.0 to 5.0.0.0

Author: ben

Gemfile

@@ -13,6 +13,6 @@ gem 'asciidoctor-pdf', '2.3.4'
 gem 'coderay', '1.1.3'
 gem 'pygments.rb', '2.3.1'
 gem 'thread_safe', '0.3.6'
-gem 'epubcheck-ruby', '4.2.6.0'
+gem 'epubcheck-ruby', '5.0.0.0'
 gem 'html-proofer', '5.0.5'
 gem 'kindlegen', '3.1.1'