Bump kramdown from 2.3.0 to 2.3.1

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

@@ -37,7 +37,7 @@ GEM
       jekyll (>= 3.8, < 5.0)
     jekyll-watch (2.2.1)
       listen (~> 3.0)
-    kramdown (2.3.0)
+    kramdown (2.3.1)
       rexml
     kramdown-parser-gfm (1.1.0)
       kramdown (~> 2.0)
@@ -67,12 +67,13 @@ GEM
     webrick (1.7.0)
 
 PLATFORMS
+  ruby
   x86_64-darwin-19
 
 DEPENDENCIES
   jekyll (~> 4.2.0)
-  jekyll-feed (~> 0.12)
-  minima (~> 2.5)
+  jekyll-feed (~> 0.15, >= 0.15.1)
+  minima (~> 2.5, >= 2.5.1)
   tzinfo (~> 1.2)
   tzinfo-data
   wdm (~> 0.1.1)