tweak CI (#35)

Author: carllerche

.github/workflows/rust.yml renamed to .github/workflows/ci.yml

@@ -1,4 +1,4 @@
-name: Rust
+name: CI
 
 on:
   push:
@@ -17,3 +17,8 @@ jobs:
       run: cargo build --verbose
     - name: Run tests
       run: cargo test --verbose
+    - name: rustfmt
+      uses: actions-rs/cargo@v1
+      with:
+        command: fmt
+        args: --all -- --check