Add preview button for request panel

Dear,

I love the feature to use plugin as part of request payload (in my test i use "Base64 - Encode File" plugin).
Also is very nice that the plugin show a "info" label instead of the result of the plugin, in this way the payload keep its readibility.

But sometimes is also usefull to see the RAW PAYLOAD REQUEST to check what we are sending to web server.

My idea is to have a button somewhere to switch between standard editor (like it is now) and its RAW counterpart.
Of course i don't mean to change the request type (that should still remain JSON in my case).

Make it sense for you?

Start at the request panel and trace how plugin-backed request payloads are rendered. Identify the existing standard editor entry point and how the request body is produced, then verify that a preview can switch to the raw payload without changing the request type. Done means the panel provides the requested toggle and displays the payload sent to the web server.

Written by the indexing model from the issue text.