Action required: Add a Renovate config

[renovate]

Hi,

You will need to add a config to this repository if you want Renovate to continue creating PRs. Renovate will soon begin skipping all repositories that don't have a valid config found, even if you've received PRs before.

To keep functionality exactly the same, you can add an empty JSON config ({}) to your repo in any of the following files: renovate.json, .github/renovate.json, .renovaterc, .renovaterc.json