Missing line breaks when copying selected text

[santiagos01]

Describe the bug

As titled. If you try to do a text selection and copy it to clipboard, the result would not have proper line breaks.

To Reproduce

Steps to reproduce the behavior:

1. Go to the example code and run it.
2. Do a text selection and try to copy the text.
3. Paste the text in clipboard.

Expected behavior

Well-formatted paragraphs according to the copied text.

Platform

Tested on the web and linux desktop, but the issue should persist across all platforms.
This is related to flutter/flutter#154253.

[santiagos01]

Related: in case anyone is looking about a similar issue with copying highlighted text, perhaps can consider to fork the flutter_highlight package and apply this change: git-touch/highlight.dart#25