Update proposal array grouping to use static methods

[jsejcksn]

The API has been modified. See:

• Convert to static factory methods tc39/proposal-array-grouping#47
• Stage 3 Criteria tc39/proposal-array-grouping#54

[zloirock]

Thanks, I'm watching this. Sure, it will be updated soon, with the rest changes from this meeting.

[jsejcksn]

Thanks, I'm watching this. Sure, it will be updated soon, with the rest changes from this meeting.

👍 Just making sure it's in the backlog.