ci: check proto format

This patch enables CI for proto files.

.github/workflows/lint.yaml

@@ -0,0 +1,49 @@
+name: lint
+
+on:
+  push:
+    branches:
+      - master
+    tags:
+      - '**'
+  pull_request:
+  workflow_dispatch:
+
+concurrency:
+  # Update of a developer branch cancels the previously scheduled workflow
+  # run for this branch. However, the 'master' branch and tag workflow runs
+  # are never canceled.
+  #
+  # We use a trick here: define the concurrency group as 'workflow run ID' +
+  # 'workflow run attempt' because it is a unique combination for any run.
+  # So it effectively discards grouping.
+  #
+  # Important: we cannot use `github.sha` as a unique identifier because
+  # pushing a tag may cancel a run that works on a branch push event.
+  group: ${{ (
+    github.ref == 'refs/heads/master' ||
+    startsWith(github.ref, 'refs/tags/') ) &&
+    format('{0}-{1}', github.run_id, github.run_attempt) ||
+    format('{0}-{1}', github.workflow, github.ref) }}
+  cancel-in-progress: true
+
+jobs:
+  protobuf:
+    runs-on: ubuntu-20.04-self-hosted
+    container:
+      image: docker.io/tarantool/testing:ubuntu-focal
+
+    steps:
+      - name: Prepare checkout
+        uses: tarantool/actions/prepare-checkout@master
+
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Install clang-format
+        run: |
+          apt-get update
+          apt-get -y install clang-format
+
+      - name: Checking protobuf syntax
+        run: clang-format --dry-run --verbose -Werror *.proto