Upgrade to GitHub-native Dependabot

.github/dependabot.yml

@@ -0,0 +1,44 @@
+version: 2
+updates:
+- package-ecosystem: bundler
+  directory: "/"
+  schedule:
+    interval: daily
+    time: "10:00"
+    timezone: Asia/Tokyo
+  open-pull-requests-limit: 99
+  ignore:
+  - dependency-name: nokogiri
+    versions:
+    - 1.11.1
+    - 1.11.2
+    - 1.11.3
+  - dependency-name: rails
+    versions:
+    - 6.0.3.5
+    - 6.0.3.6
+  - dependency-name: listen
+    versions:
+    - 3.4.1
+    - 3.5.0
+  - dependency-name: bootsnap
+    versions:
+    - 1.6.0
+    - 1.7.0
+    - 1.7.1
+    - 1.7.2
+    - 1.7.3
+  - dependency-name: puma
+    versions:
+    - 5.2.0
+    - 5.2.1
+  - dependency-name: spring
+    versions:
+    - 2.1.1
+  - dependency-name: rails-controller-testing
+    versions:
+    - 1.0.5
+  - dependency-name: dotenv-rails
+    versions:
+    - 2.7.6
+  rebase-strategy: disabled