Re-add formatting CI check which was accidentally removed (#60)

* Re-add formatting which was accidentally removed

* Whoops, indenting was already correct

* Try even simpler case

.github/workflows/ci.yml

@@ -39,13 +39,17 @@ jobs:
       - name: Make mask available globally (windows)
         run: copy ./target/debug/mask.exe ~/.cargo/bin/
         if: matrix.platform == 'windows-latest'
-      - name: Make mask available globally (linux)
+      - name: Make mask available globally (linux / mac)
         run: cp ./target/debug/mask ~/.cargo/bin
-        if: matrix.platform == 'ubuntu-latest'
-      - name: Make mask available globally (mac)
-        run: cp ./target/debug/mask ~/.cargo/bin
-        if: matrix.platform == 'macos-latest'
+        if: matrix.platform != 'windows-latest'
       - name: Run tests
         run: cargo test --frozen
 
-
+  format:
+    name: Format
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout master
+        uses: actions/checkout@master
+      - name: Verify formatting is correct
+        run: cargo fmt --all -- --check