ci: setup Renovate (#9)

Author: Djaytan

.github/renovate.json5

@@ -0,0 +1,28 @@
+{
+  $schema: 'https://docs.renovatebot.com/renovate-schema.json',
+  extends: [
+    'config:best-practices',
+    'schedule:monthly',
+    'security:openssf-scorecard'
+  ],
+  configMigration: true,
+  labels: [
+    't:dependencies'
+  ],
+  lockFileMaintenance: {
+    enabled: true,
+    extends: [
+      'schedule:monthly'
+    ]
+  },
+  osvVulnerabilityAlerts: true,
+  prConcurrentLimit: 50,
+  prHourlyLimit: 20,
+  semanticCommits: 'enabled',
+  vulnerabilityAlerts: {
+    enabled: true,
+    labels: [
+      't:security'
+    ]
+  }
+}