add note about webapp context path for REST API examples

The document at https://help.sonatype.com/repomanager3/rest-and-integration-api/script-api/managing-and-running-scripts provides examples for managing scripts in NXRM3. If the NXRM 3 server is configured with a context path, then the examples all return error 404.

Suggestion: Include a note near top of document that the correct url is:
http://localhost:8081/[context-path/]service/rest/v1/script

Such that if the nexus-context-path property is configured in etc/nexus.properties, then the context-path must be specified in the script request.