Target netstandard2.0 ?

[njlr]

I was wondering if there's a way to define tests / test lists in a netstandard2.0 library.

Expecto as it is now appears to only target net6.0. This can be a challenge if we want to share tests across various targets, such as in Fable projects.

Any ideas?

Also happy to send some PRs to enable this given some guidance. Thanks!