Add additional documentation to MSBuild Properties

[loligans]

I noticed today that some of the properties are not documented and I'd like to create a PR to address it. Is this project still maintained?

For the MSBuild property EnableDefaultCompileItems the extension says

I don't know anything about the EnableDefaultCompileItems property, but it's defined in this project (or a project it imports); you can override its value by specifying it here.

I found the documentation for this property and many others that are not documented in this extension here:
https://docs.microsoft.com/en-us/dotnet/core/project-sdk/msbuild-props#enabledefaultcompileitems