Upgrade to GitHub-native Dependabot

Author: dependabot-preview[bot]

.dependabot/config.yml

@@ -0,0 +1,30 @@
+version: 2
+updates:
+- package-ecosystem: bundler
+  directory: "/"
+  schedule:
+    interval: daily
+  open-pull-requests-limit: 10
+  versioning-strategy: increase-if-necessary
+  ignore:
+  - dependency-name: rails
+    versions:
+    - 6.1.3.1
+- package-ecosystem: bundler
+  directory: "/test/rails_52"
+  schedule:
+    interval: daily
+  open-pull-requests-limit: 10
+  versioning-strategy: increase-if-necessary
+  ignore:
+  - dependency-name: rails
+    versions:
+    - 5.2.4.5
+    - 5.2.5
+    - 6.1.3.1
+- package-ecosystem: bundler
+  directory: "/test/rails_61"
+  schedule:
+    interval: daily
+  open-pull-requests-limit: 10
+  versioning-strategy: increase-if-necessary