feat: Improved adapter and persister registration

[offirgolan]

Adapters

import { XHRAdapter, FetchAdapter } from '@pollyjs/core';

// Register the xhr adapter so its accessible by all future polly instances
Polly.register(XHRAdapter);

polly.configure({
  adapters: ['xhr', FetchAdapter]
});

Persister

import { LocalStoragePersister, RESTPersister } from '@pollyjs/core';

// Register the local-storage persister so its accessible by all future polly instances
Polly.register(LocalStoragePersister);

polly.configure({
  persister: 'local-storage'
});

polly.configure({
  persister: RESTPersister
});

[jasonmit]

LGTM, just docs need to be updated to reflect the changes

[jasonmit]

Are there tests asserting disconnect on configure (quick grep didn't find anything)? Would be useful if there isn't.

[offirgolan]

Done.

[jasonmit]

Might be useful for it to take a factory also (but not necessary).