Support render arrays using render properties as render children

Hi !

When using single directory components, I cannot render them in ui_examples. It seems thats props and slots get prefixed with # in ExampleSyntaxConverter, preventing them from being rendered properly.

Edit : here's a sample of the yaml for the rendered elements :

render:
  - type: html_tag
    tag: 'h1'
    value: 'Title'
  - type: component
    component: 'theme_name:button'
    props:
      type: primary
      title: ''
      tag: 
      text: 'Link title
      url: 'https://www.link-url.com'
      target: '_blank'

I found a workaround for this, by adding this piece of (untested) code :

# ExampleSyntaxConverter.php:59

protected function convertRenderArray(array $renderable): array {
    foreach ($renderable as $property => $value) {
      if (in_array($property, ['props', 'slots'])) {
        continue;
      }
// ...
  }
// ...
}

Have I missed something ? If not, I'll submit a MR with said changes.

Thanks,