Add `che.properties` to Documentation

[tolusha]

Is your task related to a problem? Please describe

The official Eclipse Che documentation lacks information on several useful configuration properties for user namespaces. Specifically, properties for adding additional labels and annotations to a user namespace are not documented. This makes it difficult for administrators to discover and utilize these important configuration options.

Describe the solution you'd like

I propose adding a new section to the documentation that details these extra configuration properties. This new content should be based on the properties found in the che.properties file [1]

[1] https://github.com/eclipse-che/che-server/blob/main/assembly/assembly-wsmaster-war/src/main/webapp/WEB-INF/classes/che/che.properties

Describe alternatives you've considered

No response

Additional context

No response

[ibuziuk]

Potentially related PR - eclipse-che/che-docs#2816