Add SonarQube Scanner tool installation demo

[KeremAR]

Describe your use-case which is not covered by existing documentation.

The demos/sonarqube folder is missing an example for tool:sonarRunnerInstallation configuration. Only server configuration is documented.

Reference any relevant documentation, other materials or issues/pull requests that can be used for inspiration.

demo page

[Aman-1206]

Hi
I’d like to work on this issue if it’s still open.
From my understanding, the current documentation covers only the SonarQube server configuration, and the missing part is a demo/example for configuring the SonarQube Scanner tool installation using JCasC (tool.sonarRunnerInstallation).
I can add a demo YAML example under demos/sonarqube/ along with a short README explanation.
Please let me know if that sounds good or if there’s anything specific you’d like me to follow.

Thanks!