Bump asciidoctor-kroki from 0.17.0 to 0.18.1 in /docs

Bumps [asciidoctor-kroki](https://github.com/Mogztter/asciidoctor-kroki) from 0.17.0 to 0.18.1.
- [Release notes](https://github.com/Mogztter/asciidoctor-kroki/releases)
- [Changelog](https://github.com/asciidoctor/asciidoctor-kroki/blob/master/RELEASE.md)
- [Commits](https://github.com/Mogztter/asciidoctor-kroki/compare/v0.17.0...v0.18.1)

---
updated-dependencies:
- dependency-name: asciidoctor-kroki
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

docs/package.json

@@ -7,6 +7,6 @@
 		"@asciidoctor/tabs": "^1.0.0-beta.3",
 		"@springio/antora-extensions": "^1.6.0",
 		"@springio/asciidoctor-extensions": "^1.0.0-alpha.9",
-		"asciidoctor-kroki": "^0.17.0"
+		"asciidoctor-kroki": "^0.18.1"
 	}
 }