ci: Check for documentation warnings

.github/workflows/ci.yml

@@ -20,6 +20,7 @@ jobs:
       - rustfmt
       - toml_validation
       - clippy
+      - docs
       - machete
       - unused_dependencies
       - test
@@ -68,6 +69,25 @@ jobs:
           components: clippy
       - run: cargo clippy --workspace --exclude protobuf --all-features --tests -- -D warnings
 
+  docs:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          submodules: 'recursive'
+      - name: install protoc
+        uses: taiki-e/install-action@v2
+        with:
+          tool: protoc@${{ env.PROTOC_VERSION }}
+      - name: install ninja
+        uses: ./.github/actions/setup-ninja
+      - uses: dtolnay/rust-toolchain@stable
+      - name: "doc --lib --all-features"
+        run: |
+          cargo doc --lib --no-deps --all-features --document-private-items
+        env:
+          RUSTDOCFLAGS: -Dwarnings
+
   machete:
     runs-on: ubuntu-latest
     steps: