Generate .index.json on the fly or remove dependency on it for packages that do not have them

[wardweistra]

Is there still a requirement (for the UI or otherwise) to have an .index.json file? When loading, for example, https://simplifier.net/packages/nictiz.fhir.nl.r4.zib2020/0.9.0-beta.1 I get 0 resources, but do get some CodeSystems:

As reported here https://chat.fhir.org/#narrow/stream/179171-dotnet/topic/Microsoft.20fhir-codegen-cli/near/383005716