Enum of interfaces

[ziadsarour]

Motivation
It would be great to have an enum of interfaces.

Developer Experience
There are 2 options, the first one being the best one I guess :

en.json

"list(interface=MyInterface, context=MyEnum)": {
    "first": {
        "title": "The 1st one"
    },
    "second": {
        "title": "The 2nd one"
    }
}

or

"list(context=MyEnum)": {
    "first(interface=MyInterface)": {
        "title": "The 1st one"
    },
    "second(interface=MyInterface)": {
        "title": "The 2nd one"
    }
}

slang.yaml

interfaces:
    MyInterface: list.*

Current behavior
Currently, both are throwing this error :

Unhandled exception:
type 'ObjectNode' is not a subtype of type 'StringTextNode' in type cast
#0      _parseMapNode.<anonymous closure> (package:slang/src/builder/builder/translation_model_builder.dart:431:52)
#1      _LinkedHashMapMixin.forEach (dart:collection-patch/compact_hash.dart:633:13)
#2      _parseMapNode (package:slang/src/builder/builder/translation_model_builder.dart:279:8)
#3      _parseMapNode.<anonymous closure> (package:slang/src/builder/builder/translation_model_builder.dart:384:20)
#4      _LinkedHashMapMixin.forEach (dart:collection-patch/compact_hash.dart:633:13)
#5      _parseMapNode (package:slang/src/builder/builder/translation_model_builder.dart:279:8)
#6      TranslationModelBuilder.build (package:slang/src/builder/builder/translation_model_builder.dart:111:28)
#7      TranslationModelListBuilder.build (package:slang/src/builder/builder/translation_model_list_builder.dart:26:48)
#8      GeneratorFacade.generate (package:slang/src/builder/generator_facade.dart:18:62)
#9      generateTranslations (file:///Users/Ziad/.pub-cache/hosted/pub.dev/slang-4.3.0/bin/slang.dart:317:34)
<asynchronous suspension>
#10     main (file:///Users/Ziad/.pub-cache/hosted/pub.dev/slang-4.3.0/bin/slang.dart:141:7)
<asynchronous suspension>