#strictKeywords

Note: x-bar does _not_ cause an error even with StrictKeywords
enabled.

-- schema.json --
{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "type": "number",
  "$dynamicAnchor": "bar",
  "foo": true,
  "x-bar": true
}
-- out/decode/extract --
ERROR:
unknown keyword "foo":
    schema.json:5:3
