Add display name and user bio to the User object

[fsvreddit]

Internally, Devvit has access to the user's display name and bio within Protos - on UserAboutResponse the display name is accessible as data.subreddit?.title and the bio as data.subreddit?.publicDescription.

It would be excellent if this was made available as part of the user object. Right now I'm using undocumented methods to go straight to the Protos to retrieve this information which feels unstable.

[kay0tickay]

@fsvreddit these were added in @next, under User.displayName and User.about. Let us know if you run into issues!