Function relayUrls

relayUrls(urls: Iterable<string>): string[]
Normalise a list of server URLs, dropping duplicates and anything that is not a server URL.
Parameters
- urls: Iterable<string>
  Server URLs as written anywhere.
Returns string[]
The normalised URLs, first occurrence first.
Example
```
relayUrls(['wss://a.example', 'wss://A.example/', 'https://b.example']); // ['wss://a.example/']
```