Add linter for when people generate proto files inside the PR (#84)

.github/workflows/protoc-lint.yml

@@ -0,0 +1,37 @@
+name: Check protobuf generated files
+
+on:
+  pull_request:
+    paths:
+      - aioesphomeapi/api_options_pb2.py
+      - aioesphomeapi/api_pb2.py
+
+jobs:
+  protoc-update:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Set up Python
+        uses: actions/setup-python@v2
+        with:
+          python-version: '3.7'
+      - name: Install protoc
+        run: |
+          sudo apt-get install protobuf-compiler
+      - name: Set up Python environment
+        run: |
+          pip3 install -e .
+          pip3 install -r requirements_test.txt
+
+      - name: Generate protoc
+        run: |
+          script/gen-protoc
+
+      - name: Check changes
+        run: |
+          if ! git diff --quiet; then
+            echo "You have altered the generated proto files but they do not match what is expected."
+            echo "Please check your local protobuf-compiler version."
+            protoc --version
+            exit 1
+          fi