[doc] updated Quick Start section for "Package and Distribute"
[doc] updated Quick Start section for "Package and Distribute"

Removed detailed steps for using `nw-builder` and listed `nwjs-builder`
and `nw-builder` side-by-side.

nwjs/nw.js,nwjs/nw.js,nwjs/nw.js,nwjs/nw.js,nwjs/nw.js,nwjs/nw.js