Adds base theming, elements & components

[l2succes]

This PR sets up the infrastructure for theming and fonts to be used for both react and react-native apps.

I also generated the module using (`react-native-builder-bob)[https://github.com/callstack/react-native-builder-bob] which help make sure the library is well set up to be consumed in a react native app.

It also sets up an example app which can be used to develop components before being integrated into the host app.

Development

To compile your changes run the following commands:

Run yarn watch
In a separate terminal, run yarn copy-watch

Make sure harvest and eclipse are in the same root directory

Changes

• Infrastructure
• Colors
• Typography
• Theming

Elements

• Box
• Flex
• Spacer

Components

• Button
• Spinner

[l2succes]

I'm still fixing a couple of things