Add prefix property of ProjectConfiguration Interface to documentation and intellisense options

[Optiq01]

I'm working on a generator that creates Angular components and just spent around 6 hours or so getting to the bottom of how to fetch the target app's / library's prefix to write into the component's selector property. Long story short the getProjects().get() and readProjectConfiguration() methods both return a prefix property which I initially didn't expect to be there from the other info I found that had me trying things like targets?.build?.options?.prefix. I eventually console.log() the entire object rather than investigating through build and options like I had been to see that there's a prefix property at the top level of the object...... so all I had to do the entire time is myProjectVar.prefix face palm. I think adding the fact that that property exists on the object we get back might help a lot of other people building component generators. I was thinking to just create a prompt for it so it can be entered manually but figured there HAD TO BE a way and it was literally that simple. I just find it odd that neither the documentation or the list of things that pop up after we hit . showing what's available on that object.