diff --git a/.github/workflows/jekyll.yml b/.github/workflows/jekyll.yml
new file mode 100644
index 0000000..5297949
--- /dev/null
+++ b/.github/workflows/jekyll.yml
@@ -0,0 +1,20 @@
+name: Jekyll site CI
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Build the site in the jekyll/builder container
+      run: |
+        docker run \
+        -v ${{ github.workspace }}:/srv/jekyll -v ${{ github.workspace }}/_site:/srv/jekyll/_site \
+        jekyll/builder:latest /bin/bash -c "chmod -R 777 /srv/jekyll && jekyll build --future"
diff --git a/Gemfile.lock b/Gemfile.lock
index d6039a9..a5fba1c 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,7 +1,7 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    activesupport (6.0.3.6)
+    activesupport (6.0.6.1)
       concurrent-ruby (~> 1.0, >= 1.0.2)
       i18n (>= 0.7, < 2)
       minitest (~> 5.1)
@@ -14,8 +14,7 @@ GEM
       execjs
     coffee-script-source (1.11.1)
     colorator (1.1.0)
-    commonmarker (0.23.10)
-    concurrent-ruby (1.3.4)
+'vendor/bundle'
     dnsruby (1.61.5)
       simpleidn (~> 0.1)
     em-websocket (0.5.2)
@@ -224,7 +223,7 @@ GEM
       jekyll (>= 3.5, < 5.0)
       jekyll-feed (~> 0.9)
       jekyll-seo-tag (~> 2.1)
-    minitest (5.14.4)
+    minitest (5.17.0)
     multipart-post (2.1.1)
     nokogiri (1.16.5)
       mini_portile2 (~> 2.8.2)
@@ -261,14 +260,14 @@ GEM
     thread_safe (0.3.6)
     typhoeus (1.4.0)
       ethon (>= 0.9.0)
-    tzinfo (1.2.10)
+    tzinfo (1.2.11)
       thread_safe (~> 0.1)
     unf (0.1.4)
       unf_ext
     unf_ext (0.0.7.7)
     unicode-display_width (1.7.0)
     yell (2.2.0)
-    zeitwerk (2.4.2)
+    zeitwerk (2.6.6)
 
 PLATFORMS
   ruby