update asciidoctor-epub3 to 1.5.0.alpha.11

Author: Sherry520

Gemfile

@@ -9,7 +9,7 @@ gem 'awesome_print'
 
 gem 'ttfunk', '1.5.1'
 gem 'asciidoctor-fb2'
-gem 'asciidoctor-epub3', '1.5.0.alpha.9'
+gem 'asciidoctor-epub3', '1.5.0.alpha.11'
 gem 'asciidoctor-pdf', '1.5.0.alpha.16'
 gem 'asciidoctor-pdf-cjk', '~> 0.1.3'
 gem 'asciidoctor-pdf-cjk-kai_gen_gothic', github: 'Sherry520/asciidoctor-pdf-cjk-kai_gen_gothic'