Possible disabling of welcome message in .net core 3.1.300

Hi @joshua-anderson @akoeplinger ,

Currently .net core 3.1 builds suffer from the annoying, log polluting welcome message (see example - https://travis-ci.org/github/gdziadkiewicz/FSharpx.Extras/jobs/691550830#L166-L177).

According to https://github.com/dotnet/sdk/issues/3828#issuecomment-557768792 since .net core 3 DOTNET_SKIP_FIRST_TIME_EXPERIENCE is no longer respected. It was resurrected as DOTNET_NOLOGO via https://github.com/dotnet/cli/pull/13275 in 3.1.300.

Please consider adding setting of this new env var to the codebase. Here a link to a build that manually turns this env var on in.travis.yaml and proves that it works as expected ( the log doesn’t contain the welcome message) - https://travis-ci.org/github/gdziadkiewicz/FSharpx.Extras/jobs/691554943

If the code is open and accepts contributions I’m willing to implement the change.