add merge scheduler workflow and readme text

.github/workflows/merge-schedule.yml

@@ -0,0 +1,31 @@
+name: Merge Schedule
+
+on:
+  pull_request:
+    types:
+      - opened
+      - edited
+      - synchronize
+  schedule:
+    # https://crontab.guru/#0_0_*_*_* run every day at 00:00
+    - cron: "0 0 * * *"
+
+jobs:
+  merge_schedule:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: gr2m/merge-schedule-action@v2
+        with:
+          # Merge method to use. Possible values are merge, squash or
+          # rebase. Default is merge.
+          merge_method: squash
+          # Time zone to use. Default is UTC.
+          time_zone: "America/Los_Angeles"
+          # Require all pull request statuses to be successful before
+          # merging. Default is `false`.
+          require_statuses_success: "true"
+          # Label to apply to the pull request if the merge fails. Default is
+          # `automerge-fail`.
+          automerge_fail_label: "merge-schedule-failed"
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

README.md

@@ -33,3 +33,19 @@ edgg, edmm, edww, eduu, edyy, event_schedules
 
 **The following jsons will be updated automatically:**
 data.json, atc_station_mappings.json
+
+## Schedules merges
+
+This repository uses [merge-schedule-action](https://github.com/gr2m/merge-schedule-action) to allow merging on [AIRAC cycles](https://www.nm.eurocontrol.int/RAD/common/airac_dates.html).
+
+In your pull requests, add a line to the end of the pull request description looking like this
+
+```
+/schedule 2022-06-08
+```
+
+If you need a more precise, timezone-safe setting, you can use an `ISO 8601` date string
+
+```
+/schedule 2022-06-08T09:00:00.000Z
+```