Make vector-icons optional

[vforvasile]

It would be cool if react-native-vector-icons was optional.

For instance, if I use custom Icons I don't want to add an additional 2MB+ of icons to my bundle.

[prscX]

Got you. I need to check for conditional import, however if you don't specify/ configure icons in xcode or android build setting then it won't bundle icons and will not increase your build size. Could you try and share your findings, please.