ci: add CI/CD job for docs

.github/workflows/build.yml

@@ -20,6 +20,30 @@ on:
         default: true
 
 jobs:
+  docs:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Install Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: '>=1.24.0-rc.1'
+          check-latest: true
+
+      - name: Build doc
+        shell: bash
+        run: |
+          make doc
+          if [[ $(git status --porcelain) ]]; then
+            echo "Docs are not up to date. Please run 'make docs' and commit the changes."
+            exit 1
+          else
+            echo "Docs are up to date."
+          fi
   build:
     if: inputs.manual || (github.repository == 'rclone/rclone' && (github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name != github.event.pull_request.base.repo.full_name))
     timeout-minutes: 60