fix: make samples work with splitted packets

Merge pull request #14 from Rutherther/packets-span

Rewrite packets string enumerator to use spans, add Injector for .NET 5+

feat: fix samples to use the bindings

feat: update samples to use UnmanagedCallersOnly entrypoint

chore: update packages to netstandard 2.1

Merge pull request #12 from Rutherther/packets

Implement custom packet serializer

feat: use packet responder in simple chat

fix: use NosSmooth.Packets in SimpleChat sample

chore: fix line endings

feat: pass event args to packet responders instead of plain packets

feat: add simple chat sample