function mixin(mixinParams) {
  class MixinSwal extends this {
    _main(params, priorityMixinParams) {
      return super._main(params, Object.assign({}, mixinParams, priorityMixinParams))
    }
  }
  // @ts-ignore
  return MixinSwal
}
Returns an extended version of `Swal` containing `params` as defaults.
Useful for reusing Swal configuration.

For example:

Before:
const textPromptOptions = { input: 'text', showCancelButton: true }
const {value: firstName} = await Swal.fire({ ...textPromptOptions, title: 'What is your first name?' })
const {value: lastName} = await Swal.fire({ ...textPromptOptions, title: 'What is your last name?' })

After:
const TextPrompt = Swal.mixin({ input: 'text', showCancelButton: true })
const {value: firstName} = await TextPrompt('What is your first name?')
const {value: lastName} = await TextPrompt('What is your last name?')

@param {SweetAlertOptions} mixinParams
@returns {SweetAlert}