Fix comments footer in post dialog

[SimoneZaza]

Description

As a user, I want to be able to write my comment while looking at the top part of the post that I'm commenting on. Real life example: I'm receiving a draft blog post that I open in the dialog. I have a comment on the first paragraph, which I want to refer to. I scroll up to copy the exact sentence, and my comment input field scrolls off the page. I want to keep it in sight so I can type and look at the part of the post that I want to focus at.

Acceptance criteria

• [ ] Keep the comment input field on the screen, scroll inside the post
• [ ] …

Additional Context

Screen shots / UX designs / data that are relevant.

Areas that will be affected

To be added during the refinement