Configure Renovate (#9)

Welcome to [Renovate](https://github.com/renovatebot/renovate)! This is an onboarding PR to help you understand and configure settings before regular Pull Requests begin.

🚦 To activate Renovate, merge this Pull Request. To disable Renovate, simply close this Pull Request unmerged.

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### Detected Package Files

 * `docker-compose.yml` (docker-compose)
 * `Dockerfile` (dockerfile)

### What to Expect

With your current configuration, Renovate will create 1 Pull Request:

<details>
<summary>chore(deps): update alpine docker tag to v20231219</summary>

  - Schedule: ["at any time"]
  - Branch name: `renovate/alpine-20231219-x`
  - Merge into: `master`
  - Upgrade alpine to `20231219`

</details>

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❓ Got questions? Check out Renovate's [Docs](https://docs.renovatebot.com/), particularly the Getting Started section.
If you need any further assistance then you can also [request help here](https://github.com/renovatebot/renovate/discussions).

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This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate).

Reviewed-on: #9
Co-authored-by: Renovate Bot <renovate@mgrote.net>
Co-committed-by: Renovate Bot <renovate@mgrote.net>

renovate.json

@@ -0,0 +1,3 @@
+{
+  "$schema": "https://docs.renovatebot.com/renovate-schema.json"
+}