Allow user to add content-type inside Slide component

[dadolun95]

Description (*)

The purpose of this pull request is to add a new "slide" component appearance called "container" as requested inside issue #384
This new appearance allow the user to insert content-type elements inside any slide.

Story

• #384 User adds content types into Slide

Manual testing scenarios (*)

1. Create a "Row" content type inside a CMS content
2. Place "Slider" content inside
3. Edit the first slide clicking on the Slider dots
4. Choose "Container" appearance
5. Save the slide
6. Place other content-type elements inside the slide

Checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• [ ] All new or changed code is covered with unit/integration tests (if applicable)
• README.md files for modified modules are updated and included in the pull request if any README.md predefined sections require an update
• All automated tests passed successfully (all builds are green)