ci(gh-actions): bash strict mode

Author: thomasleplus

.github/workflows/automerge.yml

@@ -15,6 +15,8 @@ jobs:
       - name: Enable auto-merge for Dependabot PRs
         shell: bash
         run: |
+          set -euo pipefail
+          IFS=$'\n\t'
           # Checking the PR title is a poor substitute for the actual PR changes
           # but as long as this is used only with dependabot PRs,
           # it should be safe to assume that the title is not misleading.