chore: configure Renovate (#1539)

Adds a config for the Renovate bot inspired by
https://github.com/pulumi/pulumi-cdk/blob/main/renovate.json5

Renovate is not currently succeeding to send working PRs to this
repository (see e.g. #1504) but
the hope is that adding this config brings us one step closer.

Makefile

@@ -203,3 +203,6 @@ test_provider:
 	@echo "== test_provider ==================================================================="
 	@echo ""
 	cd provider && go test -v -short ./... -parallel $(TESTPARALLELISM)
+
+renovate::
+	@echo "re-computing dependent files is not implemented yet"

renovate.json5

@@ -0,0 +1,15 @@
+{
+  $schema: "https://docs.renovatebot.com/renovate-schema.json",
+  extends: ["github>pulumi/renovate-config//default.json5"],
+  packageRules: [
+    {
+      // Update metadata when aws-native is bumped.
+      matchDatasources: ["npm"],
+      matchPackageNames: ["@pulumi/aws-native"],
+      postUpgradeTasks: {
+        commands: ["make renovate"],
+        executionMode: "branch", // Only run once.
+      },
+    },
+  ]
+}