ci: include rc testing steps in checkboxes with github release afterward (#576)

Author: zimeg

.github/workflows/release.yml

@@ -110,11 +110,19 @@ jobs:
           PR_BODY=$(cat <<EOF
           ### Summary
 
-          Release v${RELEASE_VERSION}. After merging, create a [GitHub Release](https://github.com/${{ github.repository }}/releases/new?tag=v${RELEASE_VERSION}&title=v${RELEASE_VERSION}) to tag and trigger the release pipeline.
+          Release v${RELEASE_VERSION}.
 
           ### Testing
 
-          Install the [dev-build](https://github.com/slackapi/slack-cli/releases/tag/dev-build) and verify changes.
+          - [ ] Confirm unit tests and E2E tests are passing on the [`main`](https://github.com/slackapi/slack-cli/commits/main) branch.
+          - [ ] Confirm unit tests and E2E tests are passing on this PR.
+          - [ ] Confirm the [dev-build](https://github.com/slackapi/slack-cli/releases/tag/dev-build) includes all commits since last release.
+          - [ ] Review open issues or PRs on the "[Next Release](https://github.com/slackapi/slack-cli/milestones)" milestone.
+          - [ ] Confirm the new version matches the expected next version.
+
+          ### Reviewers
+
+          After merging, create a [GitHub Release](https://github.com/${{ github.repository }}/releases/new?tag=v${RELEASE_VERSION}&title=v${RELEASE_VERSION}) to tag the new version.
 
           ### Requirements