How to set ROS_PACKAGE_PATH environment variable before starting debug environment in VSCode?

(I maintain the Microsoft VSCode ROS extension.) The extension inherits most of the environment from the ROS environment it is launched from, so if you need to set environment variables (or relocate ROS), you can set them in a terminal and launch code from the terminal.

I create a feature request - https://github.com/ms-iot/vscode-ros/issues/646, and assigned it to our 0.8.0 which I'm working on now.