github: add automated PR checklist

.github/workflows/pr_checklist.yml

@@ -0,0 +1,42 @@
+# Copyright Materialize, Inc. and contributors. All rights reserved.
+#
+# Use of this software is governed by the Business Source License
+# included in the LICENSE file at the root of this repository.
+#
+# As of the Change Date specified in that file, in accordance with
+# the Business Source License, use of this software will be governed
+# by the Apache License, Version 2.0.
+name: PR Checklist
+
+on:
+  pull_request:
+    types: [opened]
+
+permissions:
+  pull-requests: write
+
+jobs:
+  checklist:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Post checklist comment
+        uses: actions/github-script@v7
+        with:
+          script: |
+            await github.rest.issues.createComment({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              issue_number: context.payload.pull_request.number,
+              body: `### Pre-merge checklist
+
+            - [ ] The PR title is descriptive and will make sense in the git log.
+            - [ ] This PR has adequate test coverage / QA involvement has been duly considered. ([trigger-ci for additional test/nightly runs](https://trigger-ci.dev.materialize.com/))
+            - [ ] If this PR includes major [user-facing behavior changes](https://github.com/MaterializeInc/materialize/blob/main/doc/developer/guide-changes.md#what-changes-require-a-release-note), I have pinged the relevant PM to schedule a changelog post.
+            - [ ] This PR has an associated up-to-date [design doc](https://github.com/MaterializeInc/materialize/blob/main/doc/developer/design/README.md), is a design doc ([template](https://github.com/MaterializeInc/materialize/blob/main/doc/developer/design/00000000_template.md)), or is sufficiently small to not require a design.
+              <!-- Reference the design in the description. -->
+            - [ ] If this PR evolves [an existing \`$T ⇔ Proto$T\` mapping](https://github.com/MaterializeInc/materialize/blob/main/doc/developer/command-and-response-binary-encoding.md) (possibly in a backwards-incompatible way), then it is tagged with a \`T-proto\` label.
+            - [ ] If this PR will require changes to cloud orchestration or tests, there is a companion cloud PR to account for those changes that is tagged with the release-blocker label ([example](https://github.com/MaterializeInc/cloud/pull/5021)).
+              <!-- Ask in #team-cloud on Slack if you need help preparing the cloud PR. -->
+            `
+            });
+