add update_dependencies job

.github/workflows/update_dependencies.yaml

@@ -0,0 +1,43 @@
+name: Update_Dependencies
+
+on:
+  push:
+    branches:
+      - cron_update_pacakges
+  schedule:
+    - cron: 0 15 * * *
+
+jobs:
+  update_dependencies:
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          fetch-depth: 1
+          ref: master
+      - uses: subosito/flutter-action@v1
+        with:
+          channel: 'beta'
+
+        # See: https://pub.dev/packages/pubspec_update
+        # 公式で yarn upgrade --latest 相当のことができるコマンドが用意されてないので、サードパーティの package を使う
+      - run: pub global activate pubspec_update
+      - run: pub global run pubspec_update:pubspec-update --force  # See: https://dart.dev/tools/pub/cmd/pub-global#running-a-script-using-pub-global-run
+      - name: edit pubspec.yaml
+        run: |
+          # NOTE: pubspec_update は「^」で管理するため。本当は package に PR 送るのが望ましい。
+          sed -i -e 's/\^//' pubspec.yaml
+      - name: create PR
+        uses: peter-evans/create-pull-request@v2
+        env:
+          GITHUB_TOKEN: ${{ secrets.REPO_SCOPED_TOKEN }}
+        with:
+          commit-message: '[Scheduled] update dependencies'
+          title: '[Scheduled] update dependencies'
+          body: |
+            Auto-generated by [create-pull-request][1]
+
+            [1]: https://github.com/peter-evans/create-pull-request
+          branch: cron_update_dependencies
+          base: master