Rjwebb/add sentiment check comments

[rjwebb]

This PR adds a feature that allows users to submit comments under the "sentiment check" section of surveys.

Changes:

• Created a new sentiment_check_comments table to store these comments
• Created a basic unstyled UI for displaying, creating and deleting (only possible if the user is the creator of the comment) sentiment check comments
• Created GET/POST/DELETE API routes to enable this
• Installed swr for fetching sentiment comments from the API

Questions for @raykyri:

• Other than the user who posted the comment, do we want anyone else to be able to delete comments? Administrators? The conversation owner?

TODO:

• Styling
• API tests - we don't have these for other parts of the app but this would be an easy place to start
• Display "Delete" button based on whether the user can delete comments
• Deleting comments should set an "is_deleted" value, i.e. this is a "soft delete"
• Admins should be able to delete comments as well as the comment creator
• Deleted comments should display a placeholder