IG Publisher should warn if NPM package contains contents outside of the specified package type

[dotasek]

The package type is a recommended field to indicate to users the types of resources the NPM package should contain.

If this field is present, the IG publisher should produce warnings if the NPM contains resources that are outside of the intended type.

For example, a conformance type IG should produce warnings if it contains example or testing resources.

[grahamegrieve]

the IG publisher only produces packages of type "IG"