Upgrade to GitHub-native Dependabot

.github/dependabot.yml

@@ -0,0 +1,56 @@
+version: 2
+updates:
+- package-ecosystem: mix
+  directory: "/"
+  schedule:
+    interval: weekly
+    time: "21:00"
+  open-pull-requests-limit: 10
+  ignore:
+  - dependency-name: ecto_sql
+    versions:
+    - 3.5.4
+    - 3.6.0
+  - dependency-name: bamboo
+    versions:
+    - 1.6.0
+    - 1.7.0
+    - 2.0.0
+    - 2.0.1
+    - 2.0.2
+  - dependency-name: timex
+    versions:
+    - 3.7.3
+  - dependency-name: tesla
+    versions:
+    - 1.4.0
+  - dependency-name: sentry
+    versions:
+    - 8.0.4
+    - 8.0.5
+  - dependency-name: excoveralls
+    versions:
+    - 0.13.4
+    - 0.14.0
+  - dependency-name: quantum
+    versions:
+    - 3.3.0
+  - dependency-name: dataloader
+    versions:
+    - 1.0.7
+    - 1.0.8
+  - dependency-name: corsica
+    versions:
+    - 1.1.3
+  - dependency-name: postgrex
+    versions:
+    - 0.15.8
+  - dependency-name: phoenix_html
+    versions:
+    - 2.14.3
+  - dependency-name: plug
+    versions:
+    - 1.11.0
+  - dependency-name: plug_cowboy
+    versions:
+    - 2.4.1