Bump jekyll-feed from 0.10.0 to 0.12.1 (#23)

Bumps [jekyll-feed](https://github.com/jekyll/jekyll-feed) from 0.10.0 to 0.12.1.
- [Release notes](https://github.com/jekyll/jekyll-feed/releases)
- [Changelog](https://github.com/jekyll/jekyll-feed/blob/master/History.markdown)
- [Commits](jekyll/jekyll-feed@v0.10.0...v0.12.1)

Author: dependabot-preview[bot]

Gemfile

@@ -20,7 +20,7 @@ gem 'jekyll-seo-tag', "~> 2.6.1"
 
 # If you have any plugins, put them here!
 group :jekyll_plugins do
-  gem "jekyll-feed", "~> 0.10.0"
+  gem "jekyll-feed", "~> 0.12.1"
   gem "jekyll-paginate"
   gem 'jemoji'
 end

Gemfile.lock

@@ -38,8 +38,8 @@ GEM
       pathutil (~> 0.9)
       rouge (>= 1.7, < 4)
       safe_yaml (~> 1.0)
-    jekyll-feed (0.10.0)
-      jekyll (~> 3.3)
+    jekyll-feed (0.12.1)
+      jekyll (>= 3.7, < 5.0)
     jekyll-paginate (1.1.0)
     jekyll-sass-converter (1.5.2)
       sass (~> 3.4)
@@ -96,7 +96,7 @@ PLATFORMS
 
 DEPENDENCIES
   jekyll (= 3.8.5)
-  jekyll-feed (~> 0.10.0)
+  jekyll-feed (~> 0.12.1)
   jekyll-paginate
   jekyll-seo-tag (~> 2.6.1)
   jemoji