[Improvement] Improve accessibility for screen reader users

• Insomnia Version: latest, 6.4.3 • Operating System: Windows 10 1809 Insomnia works fairly well out of the box, since most elements read correctly, but there are some things that could be improved. All testing done with the [NVDA screen reader]( Offscreen content is still visible to screen readers There is some content that is visually hidden that still shows up for me with NVDA. After the preview pane that shows the received response, I'm seeing the following: 1. A <h2>loading</h2>, followed by a "cancel request button" 2. Some sort of find dialog that shows "No match :(" if no matches are found. This field also keeps stealing keyboard focus periodically, making it harder to use the app. 3. Some extra information about recently received responses, e.g "The request has succeeded. 1203.000 milliseconds Read 73.4 KB Content" Contents of editable fields can't be read Nothing is announced when using t…