Add a "sample image edition" page

[sveetch]

Feature Request

Is your feature request related to a problem or unsupported use case? Please describe.

There is many possibilities about image elements edition in CKEditor and it would need a dedicated page to demonstrate how they work and to do them properly.

Describe the solution you'd like During development #594 i did a new basic page to test and demonstrate possibilities (see screenshot below). We should add it as a new page in demo-site. This means creating a new page and fill it with proper contents from create_demo_site command.

Describe alternatives you've considered We could just add it as a static page but this will only demonstrate images behaviors, not howto edition them.

Discovery, Documentation, Adoption, Migration Strategy

Content structure

Content render

Do you want to work on it through a Pull Request? Yep.