CICD: Add 'cargo fmt' check

.github/workflows/CICD.yml

@@ -27,7 +27,12 @@ jobs:
         toolchain: ${{ env.MIN_SUPPORTED_RUST_VERSION }}
         default: true
         profile: minimal # minimal component installation (ie, no documentation)
-        components: clippy
+        components: clippy, rustfmt
+    - name: Ensure `cargo fmt` has been run
+      uses: actions-rs/cargo@v1
+      with:
+        command: fmt
+        args: -- --check
     - name: Run clippy (on minimum supported rust version to prevent warnings we can't fix)
       uses: actions-rs/cargo@v1
       with: