[Feature req] Add APIs for popup opened, closed callback

[pgarciaegido]

We are coming from here

https://github.com/CrossMint/crossmint-client-sdk/pull/28#discussion_r810521805

Let's think a bit more in detail how do we want our Button's api to look like

[alfonso-paella]

Edited the title to reflect what I understood this was about. If I misunderstood, let me know!