chore(deps): update squidfunk/mkdocs-material docker tag to v9.5.6 (#10)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [squidfunk/mkdocs-material](https://github.com/squidfunk/mkdocs-material) | final | patch | `9.5.5` -> `9.5.6` |

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### Release Notes

<details>
<summary>squidfunk/mkdocs-material (squidfunk/mkdocs-material)</summary>

### [`v9.5.6`](https://github.com/squidfunk/mkdocs-material/releases/tag/9.5.6): mkdocs-material-9.5.6

[Compare Source](https://github.com/squidfunk/mkdocs-material/compare/9.5.5...9.5.6)

-   Fixed [#&#8203;6700](https://github.com/squidfunk/mkdocs-material/issues/6700): Missing styles for Mermaid.js labels with Markdown

</details>

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### Configuration

📅 **Schedule**: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined).

🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied.

♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 **Ignore**: Close this PR and you won't be reminded about this update again.

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 - [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check this box

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This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate).
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Reviewed-on: #10
Co-authored-by: Renovate Bot <renovate@mgrote.net>
Co-committed-by: Renovate Bot <renovate@mgrote.net>

Dockerfile

@@ -1,4 +1,4 @@
-FROM squidfunk/mkdocs-material:9.5.5@sha256:9aad7af2f62950826f57928e984ea8aa77a561f67b7f5fc251ced67d52a2a5fe
+FROM squidfunk/mkdocs-material:9.5.6@sha256:a4a2029fdf524f0c727852e492cd2bbae30cc9471959da60d7dc46bf565a521b
 
 # Beispiel; https://squidfunk.github.io/mkdocs-material/getting-started/
 # hadolint ignore=DL3013