chore: Configure Renovate (#12)

* Add renovate.json

* Update Renovate configuration to base and disable dashboard

* Update Renovate configuration schema and extends

---------

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>
Co-authored-by: Justin Beckwith <justin.beckwith@gmail.com>

Author: renovate[bot]

renovate.json

@@ -0,0 +1,6 @@
+{
+  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
+  "extends": [
+    "local>promptfoo/renovate-config"
+  ]
+}