Serializing AxiosError customProps

[marcvincenti]

Is your feature request related to a problem? Please describe.

When using AxiosError.from I can pass some custom properties.
However, this custom properties are not serialized when using some libraries such as Pino.

Describe the solution you'd like

I would like to be able to get my custom properties into the json object when using AxiosError.toJSON.

Describe alternatives you've considered

No response

Additional context/Screenshots

No response