MAE-54 Insert a link to media file via WYSIWYG

[OndraM-Kentico]

Motivation

Allow marketers easily add link to an image or another media type from Media libraries via Rich text editor.

Checklist

• [x] Code follows coding conventions held in this repo
• [x] Automated tests have been added
• [x] Tests are passing
• [ ] Docs have been updated (if applicable)
• [ ] Temporary settings (e.g. variables used during development and testing) have been reverted to defaults