Add dependabot.yml to monitor outdated dependencies (#651)

Signed-off-by: Craig Perkins <[email protected]>

.github/dependabot.yml

@@ -0,0 +1,18 @@
+version: 2
+updates:
+  - package-ecosystem: "gradle"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    commit-message:
+      prefix: "dependabot:"
+    ignore:
+      # For all packages, ignore all major versions to minimize breaking issues
+      - dependency-name: "*"
+        update-types: ["version-update:semver-major"]
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    commit-message:
+      prefix: "dependabot:"