[Typescript Angular] support for wildcard in definition property

Description

When a wildcard is used as property key such as

...
"_dict_person": {
            "properties": {
                "*": {
                    "type": "object",
                    "additionalProperties": {
                        "$ref": "#/definitions/Person"
                    }
                }
            },
            "type": "object"
        },
...

Generated code isn't correct:

...
export interface DictPerson { 
    ?: { [key: string]: Person; };
}
...

Swagger-codegen version

2.4.28

Swagger declaration file content or url

https://gist.github.com/gautierrog/3ec437297f1d43c8b39ea9af3fa9b658

Command line used for generation

java -jar swagger-codegen-cli.jar generate \                                                                                 🐟  
      -l typescript-angular \
      -i http://localhost:5000/api/v1/swagger.json \
      --additional-properties "ngVersion=14.2.7" \
      -o ./sample-client

Use the supplied Swagger declaration and the posted typescript-angular generation command to reproduce the invalid ? property. Trace the typescript-angular generator and templates responsible for definition properties; done means the wildcard input produces valid TypeScript without the malformed property name.