Adding Support for env Terminal Option

[dhkatz]

This adds support for the env option that exists in the TerminalOptions interface. This allows users to add more complex custom terminals such as MSYS2 that require certain environment variables to be set in order to properly open in the correct working directory.

This is a common use case for this option, often used to integrate MSYS2 terminal with VSCode:

    "shellLauncher.shells.windows": [
        {
            "shell": "C:\\msys64\\usr\\bin\\bash.exe",
            "label": "MSYS2",
            "args": ["--login", "-i"],
            "env": {
                "MSYSTEM": "MINGW64",
                "CHERE_INVOKING": "1"
            }
        }
    ]

[dhkatz]

In the event the author of this extension does not merge this pull request, I've added a release to my fork which you can manually install.

Install the .vsix file manually, easy to search if you do not know how.

https://github.com/DoctorJew/vscode-shell-launcher/releases/tag/v0.3.0

[Tyriar]

Looks great, thanks 😃