Implement missing presence fields.

Summary

Discord now exposes multiple activities as well as desktop, mobile, and web client statuses.

Details

As per Quahu, the new presence looks like this:

As per Sinister Rectus, the new status fields are as follows:

client_status : {
        desktop : undefined or string
        mobile : undefined or string
        web : undefined or string
    }

Notes

As useless as the Discord docs are, there might be something of value in the presence update section.