chore: move Renovate config to root (#77)

## Summary
- move Renovate config to the repository root
- enable Renovate fork processing

## Verification
- `jq empty renovate.json`

Author: Boshen

renovate.json

@@ -0,0 +1,5 @@
+{
+  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
+  "extends": ["github>Boshen/renovate"],
+  "forkProcessing": "enabled"
+}