App builds with NativeBase carry needless bloat

## I have gone through these following points

- [x] Check latest documentation: https://docs.nativebase.io/
- [x] Check for existing open/closed issues for a possible duplicate before creating a new issue: https://github.com/GeekyAnts/NativeBase/issues
- [x] Use the latest NativeBase release: https://github.com/GeekyAnts/NativeBase/releases
- [n/a] Check examples from NativeBase KitchenSink https://github.com/GeekyAnts/NativeBase-KitchenSink
- [n/a] For discussion purpose make use of NativeBase Slack: http://slack.nativebase.io/
- [n/a] For queries related to theme, check [Theme Variables](https://docs.nativebase.io/docs/ThemeVariables.html) from Docs and live NativeBase Theme Editor http://nativebase.io/customizer/

## Issue Description

I would like to see Native Base reduce its build bloat, by offering the option to omit unused resources, like the dozen icon fonts.

#### node, npm, react-native, react and native-base version, expo version if used, xcode version

n/a

#### Expected behaviour

Smaller builds.

#### Actual behaviour

Larger builds 😉

#### Steps to reproduce

Run `react-native link` on a project with Native Base installed and behold!

#### Is the bug present in both iOS and Android or in any one of them?

It's present in both, but Native Base has the even-worse behavior for Android of installing copies of the fonts into the versioned `/android` directory.

#### Any other additional info which would help us debug the issue quicker.

###Important

If you want your issue to be looked at quicker, attach a snack reproducible with your issue. Makes it easier for us!