Update buf CI GitHub action (#933)

Update the GitHub action to use `buf-action`. This has improved support
for handling syncing GitHub repositories with the BSR. See the [default
behaviour](https://github.com/bufbuild/buf-action?tab=readme-ov-file#default-behavior).
Changes include:
- On each push to the repository the event will be synced. This includes
the git-metadata of the push.
- Formatting has been added as a check.

.github/workflows/buf-ci.yaml

@@ -0,0 +1,28 @@
+name: Buf CI
+on:
+  push:
+    paths:
+      - '**.proto'
+      - '**/buf.yaml'
+      - '**/buf.lock'
+      - '**/buf.md'
+      - '**/README.md'
+      - '**/LICENSE'
+      - '.github/workflows/buf-ci.yaml'
+  pull_request:
+    types: [opened, synchronize, reopened, labeled, unlabeled]
+  delete:
+permissions:
+  contents: read
+  pull-requests: write
+jobs:
+  buf:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: bufbuild/buf-action@v1
+        with:
+          input: proto
+          breaking_against: 'buf.build/connectrpc/conformance'
+          token: ${{ secrets.BUF_TOKEN }}
+