Add tests with type=array, items=[a list of schemas], and uniqueItems=true

[Zac-HD]

python-jsonschema/hypothesis-jsonschema#22 points out that I'm not handling this case, and I try to move tests upstream whenever I can 😄

This should include a number of schemas that both do and do not have any matching instances; empty and non-empty lists of items; false, true, and more specific additionalItems keywords; and overlapping or non-overlapping items/additionalItems keywords.

I'll offer this around as a mentored issue for Hacktoberfest, and if nobody I know is interested I should get to it myself in a few weeks.

[Julian]

Sounds good to me!

[Zac-HD]

I was thinking more of cases where the value of the items keyword was an array of schemas, for example:

{
    "type": "array",
    "items": [{"type": "boolean"}, {"type": "boolean"}],
    "additionalItems": {"type": "boolean"},
    "uniqueItems": true
}

Matches only [true, false] or [false, true] - and nothing else.

[Julian]

Ah, got it! Yes should change the title again (in a bit)