chore(deps): update dependency markdownlint-cli to v0.28.1 (#32)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [markdownlint-cli](https://github.com/igorshubovych/markdownlint-cli) | minor | `0.27.1` -> `0.28.1` |

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### Release Notes

<details>
<summary>igorshubovych/markdownlint-cli</summary>

### [`v0.28.1`](https://github.com/igorshubovych/markdownlint-cli/releases/v0.28.1)

[Compare Source](https://github.com/igorshubovych/markdownlint-cli/compare/v0.28.0...v0.28.1)

-   Fix outdated reference to `rc` (thanks [@&#8203;shhdgit](https://github.com/shhdgit)!)

### [`v0.28.0`](https://github.com/igorshubovych/markdownlint-cli/releases/v0.28.0)

[Compare Source](https://github.com/igorshubovych/markdownlint-cli/compare/v0.27.1...v0.28.0)

-   Add `--json` option to output results in JSON format
-   Switch `rc` dependency to `run-con` to address `CVE-2020-7788`
-   Update all dependencies via `Dependabot`

</details>

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

Reviewed-on: docker/markdownlint-cli#32
Co-authored-by: Renovator Bot <renovator@rknet.org>
Co-committed-by: Renovator Bot <renovator@rknet.org>

Dockerfile

@@ -9,7 +9,7 @@ LABEL org.opencontainers.image.documentation="https://gitea.rknet.org/docker/mar
 
 ARG BUILD_VERSION
 # renovate: datasource=npm depName=markdownlint-cli
-ENV MARKDOWNLINT_VERSION="${BUILD_VERSION:-0.27.1}"
+ENV MARKDOWNLINT_VERSION="${BUILD_VERSION:-0.28.1}"
 
 ENV FORCE_COLOR=true \
     NPM_CONFIG_LOGLEVEL=error