Add additional dependabot config for private gem and docker repos

.github/dependabot.yml

@@ -1,7 +1,37 @@
 version: 2
+registries:
+  docker-registry-eu-gcr-io:
+    type: docker-registry
+    url: https://eu.gcr.io
+    username: _json_key
+    password: "${{secrets.DOCKER_REGISTRY_EU_GCR_IO_PASSWORD}}"
+
+  github-org-private:
+    type: git
+    url: https://github.com
+    username: x-access-token
+    password: "${{secrets.GIT_HUB_ROBOT_TOKEN}}"
+
+  github-org-ruby-private:
+    type: rubygems-server
+    url: https://rubygems.pkg.github.com/gocardless
+    username: gocardless-robot-readonly
+    password: "${{secrets.GIT_HUB_ROBOT_TOKEN}}"
+
 updates:
 - package-ecosystem: bundler
   directory: "/"
   schedule:
     interval: daily
   open-pull-requests-limit: 10
+  insecure-external-code-execution: allow
+  registries:
+    - github-org-private
+    - github-org-ruby-private
+- package-ecosystem: docker
+  directory: "/"
+  schedule:
+    interval: daily
+  open-pull-requests-limit: 10
+  registries:
+    - docker-registry-eu-gcr-io