Unknown project name in "Running Your First Environment"

[tisonkun]

On this page, we write:

You can use ssh .envd to attach to the environment if you exit from the shell.

envd@588f26349c61 $ exit
$ ssh demo.envd
envd@588f26349c61 $ # You are in the environment again!

So demo is the name of the project. But from the page it doesn't explain where we configure such a name.

cc @gaocegege @VoVAllen @kemingy

[gaocegege]

Yeah, we should add doc for this.