Ignore /build from npm

[teyou]

Hi,

Currently /Example/ios/build/ & /Example/android/app/build/ took quite a lot of space whenever we run npm install this package.
Possible to ignore this from the npm?

[stephanebachelier]

This package installed as node modules takes 177.4 Mb, with 167Mb for Example folder.

I don't think it's needed to provide Example folder when you install with npm.

[stephanebachelier]

See #70