Add buf-based proto linting workflow in CI

Signed-off-by: Thane Thomson <connect@thanethomson.com>

.github/workflows/proto-lint.yml

@@ -0,0 +1,21 @@
+name: Protobuf Lint
+on:
+  pull_request:
+    paths:
+      - 'proto/**'
+  push:
+    branches:
+      - master
+    paths:
+      - 'proto/**'
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    steps:
+    - uses: actions/checkout@v3
+    - uses: bufbuild/buf-setup-action@v1.1.0
+    - uses: bufbuild/buf-lint-action@v1
+      with:
+        input: 'proto'