SpeakingMap is not in the generated documentation

[iliazeus]

Please describe the problem you are having in as much detail as possible:

https://discordjs.github.io/voice/classes/voicereceiver.html#speaking

VoiceReceiver.speaking is documented to be a SpeakingMap, but there are no docs for SpeakingMap itself.

Further details:

• @discordjs/voice version: 0.6.0
• Priority this issue should have – please be realistic and elaborate if possible: same as all documentation issues, probably