As a designer I want to add a placeholder component

[tilmx]

As a designer I want to add a placeholder component so I can easily experiment with new component designs on a page.

Acceptance criterias:

1. I can add placeholder image (e.g. PNG, JPG) to a page
2. I can arrange the placeholder in the same way as other components (except properties, of course)
3. I can delete the placeholder

Note: We could internally handle the placeholder images with a image component of the component library

The placeholder component should support the following events:

• click
• hover
• TODO