Add getProvider function

[friedger]

Is your feature request related to a problem? Please describe.
When I have more than one extension installed, it is confusing which extension popups first.

Describe the solution you'd like
The library should provide a function that determines which extension to use, similar to https://github.com/friedger/stacks-send-many/blob/main/src/lib/getProvider.ts

Describe alternatives you've considered
Let the user experience bad UX

Additional context
Especially with asigna, users will have usually at least two extension installed.

Credits go to @hozzjss

[janniks]

The popup first should be fixed by selecting providers via the connect-ui. If developers don't want to use the UI, that's fine. But this implementation seems very strict. There might be more multisig providers, users trying to use leather may not have the provider set, etc.

The getProviderFromId(string) function can be used to make it easier for site to use an exact provider — does that help?

[janniks]

I feel this is an important issue so I'd like to chat more and get it right! Will think about it more

[hozzjss]

If there's a way to select the provider on log in through the popup or at least if there was a walletProvider property in the profile for each wallet then we might be able to have a solution, current wallets just fight over the StacksProvider global variable, both devs and users are frustrated by this inconsistency, not saying that this is the connect library's fault, I just wanna point out that there must be some consistency between wallets so that the UX can be consistent