feat: support mongodb array update operator $[]

[kfritsch]

fixes #378

This pr adds support for the mongodb array update operator $[] by updating mongo-object to the newest version. mongo-object received an update lately specifically to support this feature in the way described in #378 (comment).

This pr only adds tests to show that the update operator works with this version of mongo-object.

Please feel free to move, change and extend the tests and edit the commit message.

[kfritsch]

While this allows validating updates using arrayFilters, it does not validate the arrayFilter specification itself, which is not even part of the update object. Not sure if this would be worth adding to the docs.

[derwaldgeist]

Any chance to get this into simpl-schema? Being able to update multiple entries in an array is not a super rare use-case.