Add a github workflow for automerger to merge main to future (#1513)

* Add a github workflow for automerger to merge main to future

* Update the comment

Author: itingliu

.github/workflows/automerge_to_future.yml

@@ -0,0 +1,18 @@
+name: Create PR to merge release branch into the main branch
+# At the end of a release cycle and the start of a new one, we may want to automatically forward all changes to the current branch (main) to the branch for the next release (future).
+# This workflow can be disabled earlier in the release cycle in the GitHub UI as described in https://docs.github.com/en/actions/managing-workflow-runs-and-deployments/managing-workflow-runs/disabling-and-enabling-a-workflow
+on:
+  schedule:
+    - cron: '0 9 * * *'
+  workflow_dispatch:
+jobs:
+  create_merge_pr:
+    name: Create PR to merge main branch into future branch
+    uses: swiftlang/github-workflows/.github/workflows/create_automerge_pr.yml@main
+    with:
+      base_branch: future
+      head_branch: main
+    permissions:
+      contents: write
+      pull-requests: write
+    if: (github.event_name == 'schedule' && github.repository == 'swiftlang/swift-foundation') || (github.event_name != 'schedule')  # Ensure that we don't run this on a schedule in a fork