message: chore: Add futures-preview packages
  Need channel-preview and 3.0 futures preview
diff: @@ -21,7 +21,8 @@ quote = "1.0.2"
  syn = "1.0.5"
  buttplug_derive = { path = "./buttplug_derive" }
  async-std = "0.99.8"
  -futures-channel = "0.2.1"
  +futures-channel-preview = "=0.3.0-alpha.18"
  +futures-preview = "=0.3.0-alpha.18"
  [lib]
  name = "buttplug"
  