propose creating a new widget that provides fido2 interoperability

[nickelskevin]

Is your feature request related to a problem? Please describe.
It would be useful to be able to authenticate in a browser using fido2 with an atsign where the private keys are on the mobile device under the control of the owner.

Describe the solution you'd like
Create a widget that can be included in any app that would allow an atsign to be used to authenticate in a browser running a flutter web application but with the private keys kept under the control of the owner.

Describe alternatives you've considered
Started off creating yet another authentication scheme and then started looking into fido2 and that seems to be doable.

[ksanty]

@nickelskevin @sachins-geekyants should we flag for discussion PR43?