[PR] Add docs about `Object` type
[PR] Add docs about `Object` type

Summary: Closes https://github.com/facebook/flow/pull/6129

Differential Revision: D7683485

Pulled By: mroch

fbshipit-source-id: 84a26cce669b81780e7acbceb87ddef695e0695e

gabelevi/flow,facebook/flow,nmote/flow,jamesgpearce/flow,jamesgpearce/flow,samwgoldman/flow,facebook/flow,jamesgpearce/flow,nmote/flow,gabelevi/flow,claudiopro/flow,popham/flow,jamesgpearce/flow,mroch/flow,facebook/flow,facebook/flow,mroch/flow,gabelevi/flow,gabelevi/flow,mroch/flow,popham/flow,popham/flow,AgentME/flow,JonathanUsername/flow,popham/flow,facebook/flow,gabelevi/flow,samwgoldman/flow,JonathanUsername/flow,mroch/flow,claudiopro/flow,AgentME/flow,nmote/flow,samwgoldman/flow,nmote/flow,AgentME/flow,JonathanUsername/flow,samwgoldman/flow,mroch/flow,popham/flow,samwgoldman/flow,JonathanUsername/flow,nmote/flow,claudiopro/flow,nmote/flow,popham/flow,mroch/flow,facebook/flow,jamesgpearce/flow,popham/flow,samwgoldman/flow,jamesgpearce/flow,JonathanUsername/flow,JonathanUsername/flow,jamesgpearce/flow,AgentME/flow,JonathanUsername/flow,gabelevi/flow,facebook/flow,AgentME/flow,mroch/flow,nmote/flow,claudiopro/flow,gabelevi/flow,samwgoldman/flow,claudiopro/flow