Support for react native functional components

[LucasBourgeois]

Hello maintainers.

Why this PR :
Ive many SVG's in a directory, in React Native, assets are loaded at buildTime.
So you must load all of them at the startup to be able to import them and add a babel transformer to make them as RN components.
The real issue with that is that it's not possible to do dynamic imports.
So a font is the main solution.

I did everything to not being dependent of an external React Native package.
Ive tested this implementation on my own project with success.

It was a little bit challenging because of those particularities:

• unicode in this repo is not unicode but an Html Entity
• encodedChar is not a unicode
• Saving an html entity in a variable in RN requires to be a string and it will not be interpreted as an Html entity.
• We can't (from my knownledge) generates multiple components because we can't dynamic imports components from a variable string...

So here is a (among unknown others) implementation of your package for ReactNative.

I would love to see this merged after all your reviews.
Im sure that it'll help many ppl.

Feel free to give me your feedback.

[jaywcjlove]

@LucasBourgeois Upgrade v4.1.0