Provide visual preview of the uploaded profile before publishing

This bug is opened as a follow-up of the Profiler server Rapid Risk Assessment (see [Risk Record bug](https://bugzilla.mozilla.org/show_bug.cgi?id=1594327)).

As part of safeguard to users accidentally uploading private or sensitive, we should consider providing a visual preview of the profile data to users.
This would allow them to:
1) actually understand what is being publicly put online
2) catch sensitive data (such as screenshots disclosing private data or unsanitized content).

CC'ing julienw for follow-up on the RRA.

┆Issue is synchronized with this [Jira Task](https://mozilla-hub.atlassian.net/browse/FP-213)