updating onboard.js library to support gnosis safe wallet

[ashachaf]

onboard.js added support to gnosis safe wallet.
in order for us to include it we need to:

1. update the onboard.js version we use to the latest one
2. add support to gnosis safe wallet:

on this file:
https://github.com/bancorprotocol/webapp/blob/master/src/api/helpers.ts

under this section:
const wallets = [...]

add this:
{ walletName: "gnosis" }