How to get a sorted result of $lookup

Question

I have a $lookup stage in an mongodb aggregation framework request that adds an array of related documents to each requested document.

  $lookup: {
    from: 'cats',
    localField: '_id',
    foreignField: 'cat',
    as: 'cats',
  }

So each document in the result has a field with an array like this:

 cats: [{ name: "cat7"),{ name: "cat2"), ...]

How can I get each array sorted e.g. by name? Is there an aggregation step for this?

 cats: [{ name: "cat2" }),{ name: "cat7" ), ...]