Merge pull request #1949 from progit/dependabot/bundler/asciidoctor-epub3-2.1.3

Update asciidoctor-epub3 requirement from 2.1.0 to 2.1.3

Author: ben

Gemfile

@@ -7,7 +7,7 @@ gem 'json', '2.7.2'
 gem 'awesome_print', '1.9.2'
 
 gem 'asciidoctor-fb2', '0.7.0'
-gem 'asciidoctor-epub3', '2.1.0'
+gem 'asciidoctor-epub3', '2.1.3'
 gem 'asciidoctor-pdf', '2.3.15'
 
 gem 'coderay', '1.1.3'