ci: configure Dependabot for Cargo and GitHub Actions (#174)

* ci: configure Dependabot for Cargo and GitHub Actions

* ci: include read-only-contract in Cargo Dependabot coverage

.github/dependabot.yml

@@ -0,0 +1,32 @@
+version: 2
+updates:
+  # Maintain Rust / Cargo dependencies
+  - package-ecosystem: "cargo"
+    directories:
+      - "/"
+      - "/crates/pdf/read-only-contract"
+    schedule:
+      interval: "daily"
+      time: "06:00"
+      timezone: "America/New_York"
+    # Consolidate updates into a single PR rather than one PR per crate
+    groups:
+      cargo-dependencies:
+        patterns:
+          - "*"
+    commit-message:
+      prefix: "chore(deps)"
+
+  # Maintain GitHub Actions workflows
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "daily"
+      time: "06:00"
+      timezone: "America/New_York"
+    groups:
+      actions:
+        patterns:
+          - "*"
+    commit-message:
+      prefix: "ci(deps)"