`--option=--value` is wrongly parsed when `option` is an array or has `narg` set

[mleguen]

const parse = require('yargs-parser')
console.log(parse('--option=--value'))

returns, as expected:

{ _: [], option: '--value' }

However:

const parse = require('yargs-parser')
console.log(parse('--option=--value', {
  array: ['option']
}))

returns:

{ _: [], option: [], value: true }

when it would be expected to return:

{ _: [], option: [ '--value' ] }

Same issue with narg: { option: 1 }.

nargs-eats-options does not change anything to this behavior.

[mleguen]

Similar issue with --option=-value too.