Bump kramdown from 1.17.0 to 2.4.0

Bumps [kramdown](https://github.com/gettalong/kramdown) from 1.17.0 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] <[email protected]>

Author: dependabot[bot]

Gemfile.lock

@@ -19,14 +19,14 @@ GEM
       thor (~> 0.19)
     colorator (1.1.0)
     colorize (0.8.1)
-    concurrent-ruby (1.1.6)
-    em-websocket (0.5.1)
+    concurrent-ruby (1.1.10)
+    em-websocket (0.5.3)
       eventmachine (>= 0.12.9)
-      http_parser.rb (~> 0.6.0)
+      http_parser.rb (~> 0)
     ethon (0.11.0)
       ffi (>= 1.3.0)
     eventmachine (1.2.7)
-    ffi (1.9.25)
+    ffi (1.15.5)
     forwardable-extended (2.6.0)
     html-proofer (3.9.3)
       activesupport (>= 4.2, < 6.0)
@@ -37,17 +37,17 @@ GEM
       parallel (~> 1.3)
       typhoeus (~> 1.3)
       yell (~> 2.0)
-    http_parser.rb (0.6.0)
+    http_parser.rb (0.8.0)
     i18n (0.9.5)
       concurrent-ruby (~> 1.0)
-    jekyll (3.8.5)
+    jekyll (3.9.2)
       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)
@@ -58,14 +58,14 @@ GEM
       sass (~> 3.4)
     jekyll-sitemap (1.2.0)
       jekyll (~> 3.3)
-    jekyll-watch (2.1.2)
+    jekyll-watch (2.2.1)
       listen (~> 3.0)
-    kramdown (1.17.0)
-    liquid (4.0.1)
-    listen (3.1.5)
-      rb-fsevent (~> 0.9, >= 0.9.4)
-      rb-inotify (~> 0.9, >= 0.9.7)
-      ruby_dep (~> 1.2)
+    kramdown (2.4.0)
+      rexml
+    liquid (4.0.3)
+    listen (3.7.1)
+      rb-fsevent (~> 0.10, >= 0.10.3)
+      rb-inotify (~> 0.9, >= 0.9.10)
     mercenary (0.3.6)
     mini_portile2 (2.4.0)
     minitest (5.14.1)
@@ -74,15 +74,15 @@ GEM
     parallel (1.12.1)
     pathutil (0.16.2)
       forwardable-extended (~> 2.6)
-    public_suffix (4.0.6)
+    public_suffix (4.0.7)
     rake (12.3.3)
-    rb-fsevent (0.10.3)
-    rb-inotify (0.10.0)
+    rb-fsevent (0.11.1)
+    rb-inotify (0.10.1)
       ffi (~> 1.0)
-    rouge (3.3.0)
-    ruby_dep (1.5.0)
-    safe_yaml (1.0.4)
-    sass (3.7.2)
+    rexml (3.2.5)
+    rouge (3.28.0)
+    safe_yaml (1.0.5)
+    sass (3.7.4)
       sass-listen (~> 4.0.0)
     sass-listen (4.0.0)
       rb-fsevent (~> 0.9, >= 0.9.4)