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>

Author: dependabot[bot]

Gemfile.lock

@@ -61,7 +61,7 @@ GEM
       jekyll-sitemap (~> 1.3)
     jekyll-watch (2.2.1)
       listen (~> 3.0)
-    kramdown (2.2.1)
+    kramdown (2.3.0)
       rexml
     kramdown-parser-gfm (1.1.0)
       kramdown (~> 2.0)