Add CI hook to check code formatting using cargo fmt --check (#18)

.github/workflows/ci.yml

@@ -28,3 +28,11 @@ jobs:
     #         - uses: actions/checkout@v2
     #         - name: cargo clippy
     #           run: cargo clippy -- -D warnings
+    # uncoment to enable format checking
+    # fmt:
+    #     runs-on: ubuntu-latest
+    #     name: Format
+    #     steps:
+    #         - uses: actions/checkout@v3
+    #         - name: cargo fmt
+    #           run: cargo fmt --check

README.md

@@ -148,6 +148,10 @@ cargo clippy
 
 Once installed, you can use the [download command](#download-input-for-a-day).
 
+### Check code formatting in CI
+
+Uncomment the `format` job in the `ci.yml` workflow to enable fmt checks in CI.
+
 ### Enable clippy lints in CI
 
 Uncomment the `clippy` job in the `ci.yml` workflow to enable clippy checks in CI.