Support the screenreader; VoiceOver; Talkback

[fabianbrandscheid]

Hi,
When I use your PDF package, no screen reader semantics are currently supported.
I created a sample page with an AppBar and your pdfrx widget displaying a simple PDF containing some text. However, no semantics are recognized for the PDF document when I enable the showSemanticsDebugger flag in MaterialApp.
Here is a screenshot for reference:

Is it possible to expose the recognized text content as semantic nodes so that screen readers can access it?

[espresso3389]

This is a feature request and no need to discuss about it.
Superseded by #639.