Augment the "Post install" dialog to allow reviewing the script

[bkhouri]

Is your feature request related to a problem? Please describe.
The extension has integration with Swiftly that, if the user decides to install swiftly, will install the Swift toolchain version that are defined in the detected .swift-version file. However, some Swift toolchain installation has a post install script. The extension prompts the user if they script should be executed, but there is no way to review the contents of the script.

Describe the solution you'd like
As a developer, I would like to review the contents of the script that will be executed before granting access.

Describe alternatives you've considered
N/A

Additional context
N/A