Display a status message in the Cross-Check Submit tab

[asfound]

Description
When the cross-check starts, in the Cross-Check: Submit tab, in the section where reviewers’ messages appear, display a status message if no one has reviewed the work yet:

• If the work has not been reviewed, display the message: "No one has reviewed your work yet."
• The message should disappear as soon as at least one review is submitted.

Additional context
This feature intends to improve both new and experienced students' experience by making the Cross-Check process more transparent. It should also help reduce the number of repetitive questions on Discord, such as:

• "Is it normal that no one has reviewed my work yet?"