Consider adding Package Validation to document binary compatibility

[bartelink]

https://devblogs.microsoft.com/dotnet/package-validation/#validation-against-baseline-package-version has been working well with me for Equinox (see jet/equinox#455)

TL;DR it fails the build if there's a binary incompatibility compared to the public API of an earlier version

Of course, there's a selfishness to my request/suggestion too: I have multiple public packages that depend on TaskSeq >= 0.4.0 and would need to reissue quite a few packages if there was to be a binary breaking change. What I like about how this scheme works is that there's a clear line in the fsproj that documents how far back the binary compatibility stretches for any given package.