Add dependabot.yml

Closes gh-138

.github/dependabot.yml

@@ -0,0 +1,25 @@
+version: 2
+
+updates:
+
+  - package-ecosystem: "gradle"
+    target-branch: "main"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+      time: "03:00"
+      timezone: "Etc/UTC"
+    ignore:
+      - dependency-name: "*"
+        update-types: [ "version-update:semver-major", "version-update:semver-minor" ]
+
+  - package-ecosystem: "gradle"
+    target-branch: "6.1.x"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+      time: "03:00"
+      timezone: "Etc/UTC"
+    ignore:
+      - dependency-name: "*"
+        update-types: [ "version-update:semver-major", "version-update:semver-minor" ]