interop: add electron transport interop ping test

node.js/electron support for webrtc transport was added in https://.com/libp2p/js-libp2p/pull/1905 & supports:
- Dialing private-to-private
- Listening private-to-private
- Dialing private-to-public

Currently blocked on the fact that all WebRTC tests are disabled: https://.com/libp2p/js-libp2p/issues/1846