run check-features during CI

.github/workflows/build.yml

@@ -30,6 +30,10 @@ jobs:
     - uses: actions/checkout@v1
       with:
         submodules: true
+    - name: Set up Python 3.x
+      uses: actions/setup-python@v2
+      with:
+        python-version: 3.x
     - uses: ruby/setup-ruby@v1
       with:
         ruby-version: 3.0
@@ -38,6 +42,9 @@ jobs:
       run: |
         gem install bundler:1.17.3
         bundle install --full-index
+        pip install python-frontmatter
+    - name: Check feature names
+      run: python3 check-features.py
     - name: Build site with jekyll
       run: |
         bundle exec jekyll build -d build