Feature request: Expose connectors utilities from the root

[NateMay]

Currently, we must import connector functions and interfaces related to connectors deeply like below:

import { UnknownWidgetParams } from 'instantsearch.js';
import connectRefinementList, {
  RefinementListConnectorParams,
  RefinementListWidgetDescription,
} from 'instantsearch.js/es/connectors/refinement-list/connectRefinementList';

Imports would be cleaner and supported by IntelliSense if they were exported through the root type system.

Desired:

import { UnknownWidgetParams, connectRefinementList, RefinementListConnectorParams, RefinementListWidgetDescription } from 'instantsearch.js