Fix images in milestones description

[Stef-Rousset]

🎩 What? Why?

This PR updates the milestone cell to allow the display of images in front if added in the description in back.

📌 Related Issues

• Fixes https://github.com/orgs/OpenSourcePolitics/projects/26/views/1?pane=issue&itemId=167238997&issue=OpenSourcePolitics%7Crelease-party-0.31%7C43

Testing

1. As an admin in the BO, go to a process > accountability > add a milestone to a result, and add an image in description (screenshot one)
2. As a user in the FO, go to the process > accountabilty > result.
3. See that the image is displayed (screenshot two)

📷 Screenshots

ONE

TWO

♥️ Thank you!