Move Markdown check to bottom as it's the most strict check

Author: sverhoeven

.github/workflows/ci.yml

@@ -28,16 +28,15 @@ jobs:
         python-version: '3.x'
     - name: Python deps
       run: pip install pyyaml
-    - name: Check all lessons
-      run: make lesson-check-all | tee check-messages.txt
-    - uses: actions/upload-artifact@v2
-      with:
-        name: check-messages
-        path: check-messages.txt
     - name: Nokogiri deps
       run: sudo apt install -y pkg-config libxml2-dev libxslt-dev
     - name: Site deps
       run: bundle install
     - name: Build site
       run: bundle exec jekyll build
-
+    - name: Check all lessons
+      run: make lesson-check-all | tee check-messages.txt
+    - uses: actions/upload-artifact@v2
+      with:
+        name: check-messages
+        path: check-messages.txt