[GHA] Checklist action (#5225)

This GHA will add the checklist that's currently in the PR template, as
a comment, on newly opened PRs.

Because it needs write access (to add the comment), it needs to run on
the `pull_request_target` action, which means you won't see the outcome
on _this_ PR, but only once it's merged in, you'll see it on subsequent
PRs - example -
https://github.com/daisy-row/vigilant-octo-umbrella/pull/51

---------

Signed-off-by: Sally MacFarlane <macfarla.github@gmail.com>

.github/pull_request_template.md

@@ -5,17 +5,4 @@
 
 ## Fixed Issue(s)
 <!-- Please link to fixed issue(s) here using format: fixes #<issue number> -->
-<!-- Example: "fixes #2" -->
-
-## Documentation
-
-- [ ] I thought about documentation and added the `doc-change-required` label to this PR if
-    [updates are required](https://wiki.hyperledger.org/display/BESU/Documentation).
-
-## Acceptance Tests (Non Mainnet)
-
-- [ ] I have considered running `./gradlew acceptanceTestNonMainnet` locally if my PR affects non-mainnet modules.
-
-## Changelog
-
-- [ ] I thought about the changelog and included a [changelog update if required](https://wiki.hyperledger.org/display/BESU/Changelog).
+<!-- Example: "fixes #2" -->

.github/workflows/pr-checklist-on-open.yml

@@ -0,0 +1,20 @@
+name: "comment on pr with checklist"
+on:
+  pull_request_target:
+    types: [ opened ]
+    branches: [ main ]
+jobs:
+  checklist:
+    name: "add checklist as a comment on newly opened PRs"
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/github-script@v5
+        with:
+          github-token: ${{secrets.GITHUB_TOKEN}}
+          script: |
+            github.rest.issues.createComment({
+              issue_number: context.issue.number,
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              body: '- [ ] I thought about documentation and added the `doc-change-required` label to this PR if [updates are required](https://wiki.hyperledger.org/display/BESU/Documentation).\n- [ ] I have considered running `./gradlew acceptanceTestNonMainnet` locally if my PR affects non-mainnet modules.\n- [ ] I thought about the changelog and included a [changelog update if required](https://wiki.hyperledger.org/display/BESU/Changelog).'
+            })