Add a runtimeconfig.json sample to generated project

[adrianoc]

this will simplify the workflow:

1. Generate project
2. Extract locally
3. dotnet build
4. dotnet run assembly.dll
5. dotnet assembly.dll

As of today to run step 6 user needs to provide assembly.runtimeconfig.json

to simplify this process we could include such file in the compressed file; in the worst case (the assembly name does not match the one used by user) user will need to rename this file to match whatever he/she passed in the command line in step 4.

[adrianoc]

I think it is possible to reuse the very same file created by the compiler in step 3

maybe we can copy that file to the root folder through a MSBUILD task.