[skip changelog] Add formatting check to "Check Protocol Buffers" workflow (#1391)

On every push and pull request that affects relevant files, check the protocol buffer files for code formatting
inconsistency.

Author: per1234

.github/workflows/check-protobuf-task.yml

@@ -79,3 +79,22 @@ jobs:
 
       - name: Lint protocol buffers
         run: task protoc:check
+
+  check-formatting:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+
+      - name: Install Task
+        uses: arduino/setup-task@v1
+        with:
+          repo-token: ${{ secrets.GITHUB_TOKEN }}
+          version: 3.x
+
+      - name: Format protocol buffers
+        run: task protoc:format
+
+      - name: Check formatting
+        run: git diff --color --exit-code