Added Directory Build and Packages.props

[thomas-mullaly]

Addresses this issue: #111

The packages one was pretty straight forward, but there's a little more nuance with the build props.

For the nuget packages, I setup a build props which consolidates some of the common package properties and the target frameworks.

For the sample and tests, I consolidated the framework version and C# nullable feature.

I'm open to suggestions on other ways of extracting common project configuration, but this seemed like an easy "low hanging fruit" consolidation.

I also updated the ignore file to ignore DS_Store files.

[ardalis]

Remove the one empty file and looks good

[KyleMcMaster]

Does the complexity around having multiple build.props come from targeting two frameworks? I was just curious if we verified that we would still be able to publish both versions. Steve and I had planned on unifying the configuration to only target .NET 8 once it is released.

[thomas-mullaly]

Does the complexity around having multiple build.props come from targeting two frameworks? I was just curious if we verified that we would still be able to publish both versions. Steve and I had planned on unifying the configuration to only target .NET 8 once it is released.

Yeah, the multiple framework versions did force my hand on needing more than one build.props. In terms of whether the packages would publish, I had no issues building the nuget packages after the change. The contents of the nuget packages had both net7 and netstandard2 assemblies, but that was the extent of my testing.

[ardalis]

@KyleMcMaster We'll see about removing netstandard support - I got some negative feedback about doing that in another popular nuget package (ardalis/SmartEnum#363)