Removed connection as it is causing many packages to be imported

[niklabh]

Maybe sdk-core should be minimalistic

Users can just use this simple snippet instead of connection function:

import { ApiPromise } from '@polkadot/api';
import { WsProvider } from '@polkadot/rpc-provider';
import { options } from '@astar-network/astar-api';

export async function connection(endpoint: string): Promise<ApiPromise> {
  const provider = new WsProvider(endpoint);
  const api = new ApiPromise(options({ provider }));

  await api.isReady;

  return api;
}

[niklabh]

Hey @bobo-k2 @sirius651 can you please review