Publish the runing WSL version

[lucasvc]

Is your feature request related to a problem? Please describe.
As WSL 2 has features that WSL 1 not, would be useful to know inside the running shell which version is and allow execution of code depending on it.

Describe the solution you'd like
Does not matter which solution is decided, but a reliable and official mechanism to get the WSL version runing on the current shell.

Describe alternatives you've considered
This proposed superuser answer. It works, it is reliaable, but seems not pretty elegant.

Additional context
N/A

[therealkenc]

/dupe #4555

[ghost]

Hi! We've identified this issue as a duplicate of another one that already exists in this repository. This specific instance is being closed in favor of tracking the concern over on the referenced thread.

Thanks for your report!