Add image upload to the FE editor

[oliverklee]

Goal

I as a user want to have an example of handling file uploads, so add image upload to the FE editor

Acceptance Criteria

• [ ] an Image can be uploaded in the FE editor
• [ ] the Tests are written
• [ ] the Tests are running fine

Additional Information

This should serve as an example of handling file uploads and FAL in the FE via Extbase.