LazyLoad CSS Background Images: Create skeleton

[CrochetFeve0251]

Subtask #5987

As some subtasks are based on some classes that other sub tasks should implements. We would require to create skeleton of empty classes with all public methods that then could be used while testing an sub-task requiring object from another or simply make sure the data flow is correct.

For that we will have to create the following classes:

• WP_Rocket\Engine\Common\ExtractCSS\Subscriber implementing WP_Rocket\EventManagement\SubscriberInterface with the following methods:
  • get_subscribed_events
  • extract_css_files_from_html(array $data): array
  • extract_inline_css_from_html(array $data): array
• WP_Rocket\Engine\Media\Lazyload\CSS\Subscriber implementing WP_Rocket\EventManagement\SubscriberInterface with the following methods:
  • get_subscribed_events
  • maybe_replace_css_images(string $html): string
  • clear_generated_css()
  • clear_generate_css_post(WP_POST $post)
  • insert_lazyload_script()
• WP_Rocket\Engine\Media\Lazyload\CSS\Admin\Subscriber implementing WP_Rocket\EventManagement\SubscriberInterface with the following methods:
  • get_subscribed_events
  • add_meta_box(array $fields)
  • maybe_add_error_notice
• WP_Rocket\Engine\Common\Cache/FilesystemCache implementing PSR-6 and with:
  • generate_url(string $url): string