examples: add dependabot config

Author: davidhewitt

.github/dependabot.yml

@@ -0,0 +1,22 @@
+version: 2
+updates:
+
+  - package-ecosystem: "cargo"
+    directory: "examples/hello-world"
+    schedule:
+      interval: "monthly"
+
+  - package-ecosystem: "cargo"
+    directory: "examples/html-py-ever"
+    schedule:
+      interval: "monthly"
+
+  - package-ecosystem: "cargo"
+    directory: "examples/namespace_package"
+    schedule:
+      interval: "monthly"
+
+  - package-ecosystem: "cargo"
+    directory: "examples/rust_with_cffi"
+    schedule:
+      interval: "monthly"