Allow replacement variables in project-config.json

[andyc2]

I would be very helpful to allow variables in the project-config.json file. For example:

{
     ...
     "linkerFlags": [
         "-Ln", "${workspaceFolder}/${name}.lbl"
     ]
}

[rolandshacks]

Agreed. Makes a lot of sense. I marked it as enhancement.

Thanks for the feedback!!