Support multiple media types under the same status code

[iongion]

Checklist

• Run pytest tests and none is failing - They failed because they were already failing
• Run ruff check flask_openapi3 tests examples and no failed.
• Run mypy flask_openapi3 and no failed.
• Run mkdocs serve and no failed.

This PR is to be able to support multiple media types for the same status code of an endpoint

# Endpoints
api = APIBlueprint(
    "default",
    __name__,
    doc_ui=True,
)

class Project(BaseModel):
    Version: str
    Environment: str


@api.get(
    "/",
    responses={
        HTTPStatus.OK: {
            "description": "Health check",
            "content": {
                # Content type
                "application/json": Project,
                "application/bson": Project,
            },
        },
    },
)
def get_home():
    """Check status.

    Gets health status of the api.
    """
    output = Project(Version="1.0.0", Environment="dev")
    return output