chore: Configure Renovate (#24)

* Add renovate.json

* Configure Renovate for Rust dependencies

---------

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>
Co-authored-by: thieman <travis.thieman@datadoghq.com>

Author: renovate[bot]

renovate.json

@@ -0,0 +1,34 @@
+{
+  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
+  "extends": [
+    "config:recommended",
+    "group:allNonMajor",
+    "schedule:weekly"
+  ],
+  "prConcurrentLimit": 5,
+  "prHourlyLimit": 2,
+  "minimumReleaseAge": "7 days",
+  "osvVulnerabilityAlerts": true,
+  "packageRules": [
+    {
+      "matchManagers": ["cargo"],
+      "versioning": "cargo"
+    },
+    {
+      "matchManagers": ["cargo"],
+      "matchCurrentVersion": "/^0\\.[0-9]/",
+      "matchUpdateTypes": ["minor"],
+      "groupName": "cargo pre-1.0 breaking updates",
+      "prBodyNotes": [
+        "**Cargo breaking update (pre-v1.0)** — `0.x` → `0.y` is a breaking change in Cargo's semver. Before merging, verify the workspace compiles and check upstream release notes for removed features or API changes."
+      ]
+    },
+    {
+      "matchManagers": ["cargo"],
+      "matchUpdateTypes": ["major"],
+      "prBodyNotes": [
+        "**Cargo major update** — Before merging, verify the workspace compiles and check upstream release notes for removed features or API changes."
+      ]
+    }
+  ]
+}