Upgrade to GitHub-native Dependabot (#140)

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

.github/dependabot.yml

@@ -0,0 +1,26 @@
+version: 2
+updates:
+- package-ecosystem: docker
+  directory: "/"
+  schedule:
+    interval: monthly
+  open-pull-requests-limit: 10
+  ignore:
+  - dependency-name: node
+    versions:
+    - ">= 11.a, < 12"
+  - dependency-name: node
+    versions:
+    - ">= 13.a, < 14"
+  - dependency-name: node
+    versions:
+    - ">= 15.a, < 16"
+  - dependency-name: alpine
+    versions:
+    - 3.13.1
+  - dependency-name: golang
+    versions:
+    - 1.15.7.pre.alpine3.12
+  - dependency-name: node
+    versions:
+    - 14.15.4.pre.alpine