doc: use snippet for rust code example and make sure rust examples run through CI (#885)

.github/workflows/rust.yml

@@ -70,6 +70,8 @@ jobs:
       run: cargo build --all-features
     - name: Run tests
       run: cargo test --all-features
+    - name: Run examples
+      run: cargo run --example simple
   macos:
     timeout-minutes: 30
     strategy: