Bump kramdown from 2.2.1 to 2.3.0

Bumps [kramdown](https://github.com/gettalong/kramdown) from 2.2.1 to 2.3.0.
- [Release notes](https://github.com/gettalong/kramdown/releases)
- [Changelog](https://github.com/gettalong/kramdown/blob/master/doc/news.page)
- [Commits](https://github.com/gettalong/kramdown/commits)

Signed-off-by: dependabot[bot] <support@github.com>

Gemfile

@@ -17,7 +17,7 @@ group :development do
   gem 'jekyll', '~>4.0'
   gem 'json', '>= 1.9'
   gem 'less', '2.4.0'
-  gem 'kramdown', '~>2.1'
+  gem 'kramdown', '~>2.3'
   gem 'RedCloth', ">= 4.3.0"
   gem 'therubyracer' # required by less
   gem 'jshintrb', '~>0.3.0'

Gemfile.lock

@@ -56,7 +56,7 @@ GEM
     json (2.3.0)
     json-schema (2.8.1)
       addressable (>= 2.4)
-    kramdown (2.2.1)
+    kramdown (2.3.0)
       rexml
     kramdown-parser-gfm (1.1.0)
       kramdown (~> 2.0)
@@ -107,7 +107,7 @@ DEPENDENCIES
   jshintrb (~> 0.3.0)
   json (>= 1.9)
   json-schema
-  kramdown (~> 2.1)
+  kramdown (~> 2.3)
   less (= 2.4.0)
   safe_yaml
   therubyracer