Decimal and float fields have a null schema

This also applies to decimal fields. Updating title and description accordingly.

Also, marking this as "Major" because including either of these field types in an entity bundle crashes the schema for that bundle with the following error. This may have changed recently due to upstream changes in Symfony, because I don't think I experienced this originally, but it was also reported in 🐛 Decimal field causes error message on custom entity Active .

The website encountered an unexpected error. Try again later.

TypeError: Symfony\Component\Serializer\Serializer::normalize(): Return value must be of type ArrayObject|array|string|int|float|bool|null, stdClass returned in Symfony\Component\Serializer\Serializer->normalize() (line 161 of /var/lib/tugboat/stm/vendor/symfony/serializer/Serializer.php).

Drupal\jsonapi_schema\Normalizer\ListDataDefinitionNormalizer->normalize(Object, 'schema_json', Array) (Line: 32)
Drupal\jsonapi_schema\Normalizer\FieldDefinitionNormalizer->normalize(Object, 'schema_json', Array) (Line: 161)
Symfony\Component\Serializer\Serializer->normalize(Object, 'schema_json', Array) (Line: 232)
Drupal\jsonapi_schema\Controller\JsonApiSchemaController->Drupal\jsonapi_schema\Controller\{closure}(Array, Object)
array_reduce(Array, Object, Array) (Line: 231)
Drupal\jsonapi_schema\Controller\JsonApiSchemaController->addFieldsSchema(Array, Object) (Line: 210)
Drupal\jsonapi_schema\Controller\JsonApiSchemaController->getResourceObjectSchema(Object, Object)
call_user_func_array(Array, Array) (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 638)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 121)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array) (Line: 97)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 181)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 76)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 53)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 28)
Drupal\Core\StackMiddleware\ContentLength->handle(Object, 1, 1) (Line: 32)
Drupal\big_pipe\StackMiddleware\ContentLength->handle(Object, 1, 1) (Line: 116)
Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1) (Line: 90)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 51)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 36)
Drupal\Core\StackMiddleware\AjaxPageState->handle(Object, 1, 1) (Line: 51)
Drupal\Core\StackMiddleware\StackedHttpKernel->handle(Object, 1, 1) (Line: 741)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)

I've learned a lot about how this module works since I posted the patch in #4. The correct approach is to provide a new normalizer class that declares supported types of decimal and float. I will open a merge request with tests shortly...