Add docstring to generated code based on schema description

[PaleNeutron]

Implement #361

Now generated method and class will have docstring based on schema field and type description

output example

class Query:
    @classmethod
    def book_id(cls, para: bookIdParas) -> bookIdFields:
        """get book id from my database"""
        arguments: Dict[str, Dict[str, Any]] = {
            "para": {"type": "bookIdParas!", "value": para}
        }
        cleared_arguments = {
            key: value for key, value in arguments.items() if value["value"] is not None
        }
        return bookIdFields(field_name="bookId", arguments=cleared_arguments)

class bookIdFields(GraphQLField):
    """my book id"""

    book_id: "bookIdGraphQLField" = bookIdGraphQLField("book_id")

    def fields(self, *subfields: bookIdGraphQLField) -> "bookIdFields":
        """Subfields should come from the bookIdFields class"""
        self._subfields.extend(subfields)
        return self

    def alias(self, alias: str) -> "bookIdFields":
        self._alias = alias
        return self