Support adding type(CustomErrorContract) to class Output at output.py

[0x73696d616f]

Describe the desired feature

Trying to create a detector for custom errors naming, as following

def _detect(self) -> List[Output]:
    results = []
    for contract in self.compilation_unit.contracts:
        if contract.file_scope.filename.relative.startswith("lib/"):
            continue

        for custom_error in contract.custom_errors_declared:
            hasEventWrongNaming = IncorrectErrorNamingDetector.detect_incorrect_naming(custom_error)
            if hasEventWrongNaming:
                info = [
                    contract,
                    custom_error,
                    " declares error with non standard name: ",
                    custom_error.name,
                    "\n",
                ]
                res = self.generate_result(info)
                results.append(res)

Getting the error

raise SlitherError(f"Impossible to add {type(add)} to the json")
slither.exceptions.SlitherError: Impossible to add <class 'slither.core.declarations.custom_error_contract.CustomErrorContract'> to the json

The Output class is missing that field:

def add(self, add: SupportedOutput, additional_fields: Optional[Dict] = None) -> None:
    if not self._data["first_markdown_element"]:
        self._data["first_markdown_element"] = add.source_mapping.to_markdown(
            self._markdown_root
        )
    if isinstance(add, Variable):
        self.add_variable(add, additional_fields=additional_fields)
    elif isinstance(add, Contract):
        self.add_contract(add, additional_fields=additional_fields)
    elif isinstance(add, Function):
        self.add_function(add, additional_fields=additional_fields)
    elif isinstance(add, Enum):
        self.add_enum(add, additional_fields=additional_fields)
    elif isinstance(add, Event):
        self.add_event(add, additional_fields=additional_fields)
    elif isinstance(add, Structure):
        self.add_struct(add, additional_fields=additional_fields)
    elif isinstance(add, Pragma):
        self.add_pragma(add, additional_fields=additional_fields)
    elif isinstance(add, Node):
        self.add_node(add, additional_fields=additional_fields)
    else:
        raise SlitherError(f"Impossible to add {type(add)} to the json")