unknown --option=value arg split when defaultOption set

[75lb]

This example correctly returns the --two=3 arg as an _unknown but the string is split into '--two' and '3'.

> const definitions = [ { name: 'file', type: String, defaultOption: true } ]
> commandLineArgs(definitions, { partial: true, argv: [ 'file', '--two=3' ] })
{ file: 'file', _unknown: [ '--two', '3' ] }

This issue is typically harmless as --two=3 and --two 3 are interchangeable. However, the correct output should be:

{ file: 'file', _unknown: [ '--two=3' ] }

[75lb]

Fixed in v5.0.0.