Add support for jsonschema 4.x

jsonschema 4.0 was released in September 2021. It's time to support it.
Only one issue to address in our tests, namely that when specifying the
'items' key for a property of type 'array', the value should be an
object, not an array of objects.

  Good:

    {
      "type": "object",
      "properties": {
        "fruits": {
          "type": "array",
          "items": { "type": "string" }
        }
      }
    }

  Bad:

    {
      "type": "object",
      "properties": {
        "fruits": {
          "type": "array",
          "items": [{ "type": "string" }]
        }
      }
    }

The docs say as much [1].

[1] https://json-schema.org/learn/miscellaneous-examples.html#arrays-of-things

Signed-off-by: Stephen Finucane <stephen@that.guru>
Closes: #64

1 files changed, 1 insertions, 1 deletions

diff --git a/tests/test_core.py b/tests/test_core.py
index bc36c92..390e61c 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -38,7 +38,7 @@ parent_fixture = {
     "name": "Parent",
     "properties": {
         "name": {"type": "string"},
-        "children": {"type": "array", "items": [{"type": "object"}]},
+        "children": {"type": "array", "items": {"type": "object"}},
     },
     "required": ["name", "children"],
 }