Add format checks to workflows (#3)

Author: ktanaka101

.github/workflows/zig.yml

@@ -22,3 +22,10 @@ jobs:
 
       - name: Run tests
         run: zig build test
+
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: goto-bus-stop/setup-zig@v2
+      - run: zig fmt --check .