Add notes about dnx

[baronfel]

Summary

Add a brief snippet about the new dnx script and how it should be packaged by distro maintainers.

Fixes dotnet/sdk#49649

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[baronfel]

@MichaelSimons / @tmds is it reasonable to add the version-independent dnx script to the host package as a recommendation? If adding to an existing package isn't allowed for reasons I'm happy to suggest a new package.

[tmds]

it reasonable to add the version-independent dnx script to the host package as a recommendation?

Yes, this sounds good to me, it's the simplest solution.

[tmds]

@baronfel we also need a symlink similar to (10).

[baronfel]

@baronfel we also need a symlink similar to (10).

of course! That's kind of a critical part of making everything Just Work ™️ . Thanks for the review.

[MichaelSimons]

Attention @dotnet/distro-maintainers

[mateusrodrigues]

If dotnet dnx is an SDK command, should dnx be packaged in the dotnet-host package rather than the dotnet-sdk-X.Y package?

e.g., if the user installs only the runtime (dotnet-runtime-X.Y), which pulls in dotnet-host, they will have a dnx script that doesn't work because there is no SDK, as I understand it.

EDIT: Now that I think about it, I guess the issue is that multiple SDK packages would then provide the same set of files, which is a problem. I'm curious, though, to know how dnx would handle the non-existence of dotnet dnx when there's no SDK installed.