update GSL to a version >=3.0.0

[saurik]

I'm sorry I didn't fill out the template, but it didn't actually seem appropriate as this package already exists... it is just 5 years old and is stuck a full major version back :(. This project already uses CMake upstream and continues to be hosted in https://github.com/microsoft/GSL.

[NeroBurner]

a PR updating the package would be very welcome.

Here is some documentation about updating a Hunter package: https://hunter.readthedocs.io/en/latest/creating-new/update.html

[NeroBurner]

closing old package request, please reopen and send PR if still interested