Migrate samples from the "sample" branch in dotnet/try

[BillWagner]

We've created this repo because the dotnet/try repository is the wrong location.

There are a few subtasks for completing this:

• [x] Bring the C# 8 exploration to this repository (See #7)
• [x] Bring the beginners samples and Pascal's triangle sample to this repo. Source is in the dotnet/try#Samples branch.
• [x] Update the last item in the dotnet/try README section on "getting started" to point to this repo.
• [x] Delete the "Samples" branch from the dotnet/try repo.

/cc @LadyNaggaga @jonsequitur

[BillWagner]

All tasks have been completed. Closing this.