.github: ensure docs are up to date in CI

This commit updates the CI configuration for Kilo to ensure that the
documentation, specifically the generated docs, are up-to-date.

Signed-off-by: Lucas Servén Marín <lserven@gmail.com>

.github/workflows/ci.yml

@@ -36,6 +36,19 @@ jobs:
     - name: Build
       run: make
 
+  docs:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up Go
+      uses: actions/setup-go@v2
+      with:
+        go-version: 1.17.1
+    - name: Build docs
+      run: |
+        make gen-docs
+        git diff --exit-code
+
   linux:
     runs-on: ubuntu-latest
     steps: