add environment variable for vscode code example

Example 1: vscode windows environment variables

"terminal.integrated.env.windows": {
    "PATH": "${env:PATH}"
},

Example 2: vscode read environment variables

{
  "type": "node",
  "request": "launch",
  "name": "Launch Program",
  "program": "${workspaceFolder}/app.js",
  "cwd": "${workspaceFolder}",
  "args": ["${env:USERNAME}"]
}