Support for Signature widgets/annotations ?

[dickverweij]

Is your feature request related to a problem? Please describe.
We use your fabulous package to show pdf's in our flutter app. We noticed that the signature widgets/annotations are not shown.

Describe the solution you'd like
support for signature widgets/annotation in the rendering
https://www.adobe.com/devnet-docs/acrobatetk/tools/DigSig/Acrobat_DigitalSignatures_in_PDF.pdf

Describe alternatives you've considered
There are no alternatives

Additional context