Advanced gradient of skeleton effect, suitable for waiting for pictures

General steps:

• A component is required, which is used as a placeholder.This placeholder component has a professional term: skeleton screen component.
  • Expose some properties: height, width, background, whether there is a flash animation.
• This is a public component that needs to be registered globally. It is recommended that such a component be defined in the vue plugin in the future.
• Use components to complete the left classified skeleton effect.