Bump kramdown from 1.17.0 to 2.3.1

Bumps [kramdown](https://github.com/gettalong/kramdown) from 1.17.0 to 2.3.1.
- [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

@@ -4,26 +4,26 @@ GEM
     addressable (2.7.0)
       public_suffix (>= 2.0.2, < 5.0)
     colorator (1.1.0)
-    concurrent-ruby (1.1.6)
-    em-websocket (0.5.1)
+    concurrent-ruby (1.1.8)
+    em-websocket (0.5.2)
       eventmachine (>= 0.12.9)
       http_parser.rb (~> 0.6.0)
     eventmachine (1.2.7)
     faraday (1.0.1)
       multipart-post (>= 1.2, < 3)
-    ffi (1.13.1)
+    ffi (1.15.0)
     forwardable-extended (2.6.0)
     http_parser.rb (0.6.0)
     i18n (0.9.5)
       concurrent-ruby (~> 1.0)
-    jekyll (3.8.7)
+    jekyll (3.9.1)
       addressable (~> 2.4)
       colorator (~> 1.0)
       em-websocket (~> 0.5)
       i18n (~> 0.7)
       jekyll-sass-converter (~> 1.0)
       jekyll-watch (~> 2.0)
-      kramdown (~> 1.14)
+      kramdown (>= 1.17, < 3)
       liquid (~> 4.0)
       mercenary (~> 0.3.3)
       pathutil (~> 0.9)
@@ -45,9 +45,10 @@ GEM
       jekyll-paginate (~> 1.1)
     jekyll-watch (2.2.1)
       listen (~> 3.0)
-    kramdown (1.17.0)
+    kramdown (2.3.1)
+      rexml
     liquid (4.0.3)
-    listen (3.2.1)
+    listen (3.5.1)
       rb-fsevent (~> 0.10, >= 0.10.3)
       rb-inotify (~> 0.9, >= 0.9.10)
     mercenary (0.3.6)
@@ -57,11 +58,12 @@ GEM
       sawyer (~> 0.8.0, >= 0.5.3)
     pathutil (0.16.2)
       forwardable-extended (~> 2.6)
-    public_suffix (4.0.5)
+    public_suffix (4.0.6)
     rb-fsevent (0.10.4)
     rb-inotify (0.10.1)
       ffi (~> 1.0)
-    rouge (3.21.0)
+    rexml (3.2.5)
+    rouge (3.26.0)
     safe_yaml (1.0.5)
     sass (3.7.4)
       sass-listen (~> 4.0.0)
@@ -78,6 +80,7 @@ PLATFORMS
 DEPENDENCIES
   jekyll-sitemap
   jekyll-theme-hydeout (~> 3.4)
+  kramdown (>= 2.3.1)
 
 BUNDLED WITH
    2.1.4