Initial package settings

[abelbraaksma]

^{(edit: belongs to both milestones v0.2.1 and v0.2.2, see commit history)}

Just getting the settings right. Apparently, in VS 2022, filling in the fields in Project Properties gets only partially saved, so this is a bit of searching around what I actually need.

First packages are done by hand, see https://www.nuget.org/packages/FSharp.Control.TaskSeq/ (that'll soon be automated as soon as this is the way I like it).

All changes for release:

• Move to netstandard2.1 and FSharp.Core.dll 6.0 (it is now 6.0.5) for better compatibility
• Get the nuget metadata and versions the way I like it :)
• Create separate readme.md to show on Nuget
• Add version history for package
• Make this part of GH Actions for auto-deploy once the version increases.