Lock html-proofer in stable version (cotes2020#178)

cotes2020 · cotes2020 · commit f9ddc96d8c6e · 2020-11-23T14:09:22.000+08:00
diff --git a/Gemfile b/Gemfile
@@ -11,7 +11,7 @@ group :jekyll_plugins do
 end
 
 group :test do
-  gem "html-proofer"
+  gem "html-proofer", "~> 3.16.0"
 end
 
 # Windows and JRuby does not include zoneinfo files, so bundle the tzinfo-data gem
