Add formatting check to GH Actions workflow

Author: BrenekH

.github/workflows/ci.yaml

@@ -38,3 +38,10 @@ jobs:
       - uses: Swatinem/rust-cache@v2
 
       - run: cargo clippy --all-targets --all-features
+
+  lint-fmt:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions@checkout@v6
+
+      - run: cargo fmt --check