Consider dropping support for netstandard2

[mikegoatly]

I'd like to understand who would be affected by the removal of netstandard2.

Note that I'm not actually planning on doing this any time soon, because I'm one of the people that actually needs netstandard2 support in an old UWP application! 😊

[PetesBreenCoding]

Not me anyway. I'd say pick a major version from when netstandard is no longer supported, continue minor fixes in the old version (if you can) for a while but eventually get to a point where you stop supporting the older version