chore: add renovate bot with toolbox dep (#17)

Co-authored-by: Averi Kitsch <akitsch@google.com>

Author: Yuan325

.github/renovate.json5

@@ -0,0 +1,34 @@
+{
+  extends: [
+    'config:recommended',
+    ':semanticCommitTypeAll(chore)',
+    ':ignoreUnstable',
+    ':separateMajorReleases',
+    ':prConcurrentLimitNone',
+    ':prHourlyLimitNone',
+    ':preserveSemverRanges',
+  ],
+  rebaseWhen: 'conflicted',
+  dependencyDashboardLabels: [
+    'type: process',
+  ],
+  packageRules: [
+    {
+      groupName: 'GitHub Actions',
+      matchManagers: [
+        'github-actions',
+      ],
+      pinDigests: true,
+    },
+  ],
+  customManagers: [
+    {
+      customType: "regex",
+      managerFilePatterns: ["/toolbox_version\\.txt$/"],
+      matchStrings: ["(?<currentValue>[\\d\\.]+)"],
+      datasourceTemplate: "github-releases",
+      packageNameTemplate: "googleapis/genai-toolbox",
+      extractVersionTemplate: "^v(?<version>.*)$",
+    }
+  ]
+}