Please add selectable text feature

[arunkenjila]

[Timo Bähr]

Flutter 3.3 introduced SelectionArea widget for that purpose. Unfortunatelly it does not have an effect on ExpandableText.

Reason:
Library is using TextSpan and RichText under the hood. This is not compatible with this new widget.

RichText(text: TextSpan(text: 'hello'))