Add relative paths `.vscode`'s `c_cpp_properties.json` and `settings.json` ...

[Scoeerg]

What's the feature:

Currently the extension generates e.g. c_cpp_properties.json with with absolute paths /home/user/ros_ws/... which can be substituted with ${workspaceFolder}.

{
  "configurations": [
    {
      "browse": {
        "databaseFilename": "${default}",
        "limitSymbolsToIncludedHeaders": false
      },
      "includePath": [
        "/opt/ros/humble/include/**",
        "/home/user/ros_ws/src/cpp_python_package/include/**",
        "/usr/include/**"
      ],
      "name": "ROS",
      "intelliSenseMode": "gcc-x64",
      "compilerPath": "/usr/bin/gcc",
      "cStandard": "gnu11",
      "cppStandard": "c++14"
    }
  ],
  "version": 4
}

and settings.json:

{
    "ros.distro": "humble",
    "python.autoComplete.extraPaths": [
        "/home/user/ros_ws//install/cpp_python_package/local/lib/python3.10/dist-packages",
        "/opt/ros/humble/lib/python3.10/site-packages",
        "/opt/ros/humble/local/lib/python3.10/dist-packages"
    ],
    "python.analysis.extraPaths": [
        "/home/user/ros_ws//install/cpp_python_package/local/lib/python3.10/dist-packages",
        "/opt/ros/humble/lib/python3.10/site-packages",
        "/opt/ros/humble/local/lib/python3.10/dist-packages"
    ],
    "files.associations": {
        "functional": "cpp"
    },
    "cmake.sourceDirectory": "/home/user/ros_ws/ros_ws/src/cpp_python_package"
}

This enables path-independent settings for any user cloning the workspace-repository.
There would be no need to re-generate the settings or any manual editing.

Why is it useful?
It would make exchanging an entire workspace between developers easy, where any developer uses the same configuration for IntelliSense, debugging, building and running - especially with large and complex setups.

My setups usually have the workspace as a parent git-repo where packages are git-submodules. I.e. it is meaningful to transfer .vscode of a workspace between developers.
Currently, I manually change the paths and push them to the workspace git-repos.

Related:

#164

In the file launch.json it should be possible to use the variable ${workspaceFolder} in the ros-launch target field.
launch.json

#129