Add Dependabot config

Author: andrewhassan

.github/dependabot.yml

@@ -0,0 +1,21 @@
+version: 2
+registries:
+  ruby-shopify:
+    type: rubygems-server
+    url: https://pkgs.shopify.io/basic/gems/ruby
+    username: ${{secrets.RUBYGEMS_SERVER_PKGS_SHOPIFY_IO_USERNAME}}
+    password: ${{secrets.RUBYGEMS_SERVER_PKGS_SHOPIFY_IO_PASSWORD}}
+  github-com:
+    type: git
+    url: https://github.com
+    username: ${{secrets.DEPENDENCIES_GITHUB_USER}}
+    password: ${{secrets.DEPENDENCIES_GITHUB_TOKEN}}
+updates:
+  - package-ecosystem: "cargo"
+    directory: "/"
+    schedule:
+      interval: weekly
+    open-pull-requests-limit: 100
+    registries: "*"
+    reviewers:
+      - "@Shopify/functions-dependabot-reviewers"