Name classes for schema URI by default

[gertvv]

The following schema (example repo):

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://example.com/schema/outer.schema.json",
  "type": "object",
  "properties": {
    "inners": {
      "type": "array",
      "items": {
        "$ref": "classpath:/com/example/inner.schema.json"
      },
    },
    "additionalInner": {
      "$ref": "classpath:/com/example/inner.schema.json"
    }
  },
  "required": [
    "inners"
  ]
}

Currently generates three classes: com.example.Outer, com.example.Inners, and com.example.AdditionalInner. I would suggest that naming the class after the schema URI (if there is one), as is done for the top-level schema, would result in more meaningful class names (com.example.Inner) and less duplication.

Follow-up to #29.