build(deps): bump kramdown from 2.3.0 to 2.4.0

Bumps [kramdown](https://github.com/gettalong/kramdown) from 2.3.0 to 2.4.0.
- [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)

---
updated-dependencies:
- dependency-name: kramdown
  dependency-type: indirect
...

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

Author: dependabot[bot]

Gemfile.lock

@@ -38,7 +38,7 @@ GEM
       jekyll (>= 3.8, < 5.0)
     jekyll-watch (2.2.1)
       listen (~> 3.0)
-    kramdown (2.3.0)
+    kramdown (2.4.0)
       rexml
     kramdown-parser-gfm (1.1.0)
       kramdown (~> 2.0)
@@ -57,7 +57,7 @@ GEM
     rb-fsevent (0.10.4)
     rb-inotify (0.10.1)
       ffi (~> 1.0)
-    rexml (3.2.4)
+    rexml (3.2.6)
     rouge (3.26.0)
     safe_yaml (1.0.5)
     sassc (2.4.0)