Add renovate configuration

### Problem statement

Other repos managed by Kubernetes team already have renovate configured (e.g. KGO https://github.com/Kong/gateway-operator/blob/main/renovate.json and KIC https://github.com/Kong/kubernetes-ingress-controller/blob/main/renovate.json)

This issue tracks the effort of adding renovate configuration in this repo

### Acceptance criteria

- [ ] Renovate is configured in ktf

Start by comparing the renovate.json files in the KGO and KIC repositories linked in the issue. Add the corresponding Renovate configuration to ktf and verify that the acceptance criterion—Renovate is configured in this repository—is met.

Written by the indexing model from the issue text.