Documentation clarifying status for C++ setup on Linux

### Description

My understanding was C++ support was withdrawn a few years ago. However, recently I think this changed.... something about CCLS? Unfortunately I haven't been able to find out what exactly needs to be done to setup. There's a lot of confusion on the small handful of Stackoverflow posts.

### Use case/motivation

Could someone please add documentation clarifying what needs to be done to get C++ and Netbeans working on Linux?

### Related issues

_No response_

### Are you willing to submit a pull request?

No

The issue names no files, tests, or documentation entry points. First establish the current C++ and CCLS setup path for NetBeans on Linux, then document the required steps and verify that a newcomer can follow them successfully.

Written by the indexing model from the issue text.