HostImportModuleDynamicallyCallback arguments undocumented

[ldanilek]

The docstring for HostImportModuleDynamicallyCallback says

The referrer contains metadata about the script/module that calls import.

but there is no argument called referrer in the example code. The arguments resource_name and host_defined_options appear in the example but are not described.

i figured out the arguments by looking at the C++ docs which passes a ScriptOrModule called referrer, which contains HostDefinedOptions and ResourceName. this could be clearer in the rust docs.