Add dependabot (#182)

Author: corest

.github/dependabot.yml

@@ -0,0 +1,30 @@
+version: 2
+updates:
+  # --- Go modules ---
+  - package-ecosystem: "gomod"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    open-pull-requests-limit: 10
+    commit-message:
+      prefix: "deps(go)"
+    labels:
+      - "dependencies"
+      - "go"
+    rebase-strategy: "auto"
+
+  # --- Docker images ---
+  - package-ecosystem: "docker"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+      day: "monday"
+      time: "06:00"
+      timezone: "UTC"
+    open-pull-requests-limit: 5
+    commit-message:
+      prefix: "deps(docker)"
+    labels:
+      - "dependencies"
+      - "docker"
+    rebase-strategy: "auto"