add (rust-libp2p) gossipsub over WebRTC to interop tests

I'm not exactly sure where to open this issue, as I also see a repo for interop tests over here: https://github.com/libp2p/interop . If I've missed where this test is, my appologies.

Right now we are seeing some connectivity challenges within rust-libp2p operating over WebRTC transport to the browser.

See

• https://github.com/libp2p/rust-libp2p/issues/3665

Work is being done to demonstrate the universal connectivity amongst libp2p implementations:

• https://github.com/libp2p/universal-connectivity/pull/3

Fixes for these issues are in the works, such as:

• https://github.com/libp2p/rust-libp2p/pull/3625

I'm looking for interop tests for this to streamline troubleshooting and development, but have not found any to support this yet. This issue proposes an interop test, particularly for Gossipsub over WebRTC between rust and js, as it's in active troubleshooting at the moment.

It appears the interop tests for pubsub cover js and go:

https://github.com/libp2p/interop/blob/ce0aa3749c9c53cf5ad53009b273847b94106d40/src/pubsub/gossipsub.ts#L8-L9

export function gossipsubTests (factory: DaemonFactory) {
  const nodeTypes: NodeType[] = ['js', 'go']

but I am having a hard time finding the test where each of the different transports are used.

Start by comparing the existing pubsub test in interop/src/pubsub/gossipsub.ts, especially its js/go node types, with the linked rust-libp2p WebRTC issue and related pull requests. Identify where transport-specific interop tests are defined, then add coverage for Gossipsub over WebRTC between Rust and JavaScript with a reproducible passing test.