Upgrade to GitHub-native Dependabot

.github/dependabot.yml

@@ -0,0 +1,26 @@
+version: 2
+registries:
+  git-github-com:
+    type: git
+    url: https://github.com
+    username: x-access-token
+    password: "${{secrets.GIT_GITHUB_COM_PASSWORD}}"
+
+updates:
+- package-ecosystem: mix
+  directory: "/"
+  schedule:
+    interval: daily
+    time: "11:00"
+  open-pull-requests-limit: 10
+  ignore:
+  - dependency-name: ex_doc
+    versions:
+    - 0.23.0
+    - 0.24.0
+    - 0.24.1
+  - dependency-name: excoveralls
+    versions:
+    - 0.13.4
+  registries:
+  - git-github-com