[All Platforms] Change the in-app volume when switching devices

[joycerice888]

I would be listening to Spotify on Alexa, but then switch to headphones on my computer. For some reason the in-app volume would automatically default to whatever the Alexa was using. It'd be much easier if you could set a default in-app volume for each of your devices to avoid the hassle of having to change the in-app volume, which cannot be controlled by headphones or such.