Add Key Resharing

[liangping]

Hello Team!

We have completed key resharing, wondering if we could submit a PR for this feature?

for more details: main...liangping:frost:resharing

[natalieesk]

Thank you for this. We're taking a look.

[liangping]

Be free to leave your feedbacks, we are happy to contribute

[natalieesk]

This is useful work thank you. We are not prioritising this at the moment but we will look at it in the near future.

[johnnynanjiang]

Hi folks,

How is this work going?

Key resharing seems to be there already as per https://frost.zfnd.org/frost.html#refreshing-shares.