Merge pull request #5 from progit/dependabot/bundler/json-2.21.1

Update json requirement from 2.9.1 to 2.21.1

Author: ben

Gemfile

@@ -3,7 +3,7 @@ source 'https://rubygems.org'
 gem 'rake', '13.4.2'
 gem 'asciidoctor', '2.0.26'
 
-gem 'json', '2.9.1'
+gem 'json', '2.21.1'
 gem 'awesome_print', '1.9.2'
 
 gem 'asciidoctor-fb2', '0.7.0'