Create an NPM package for React Native

An example repo of how to create an NPM package for use in other projects. In this case, React Native.

Steps

Create a new project which includes a package.json. In this case we're using expo so we can test then release.
```
npx create-expo-app npm-rn-counter
```
Define then export the components, functions, constants we want to expose from our package.
- This package exports from ./src/lib/Counter.js which exports 1 component, constant, function each.
Add necessary keys to package.json to configure npm.
- Version package "version": "1.0.51".
- Include the ./src and ./README.md with "files": [].
- Define entry point for modules in this package "main": "index.js".
- Info which shows up on the npm.com registry web page "repository": {}.
Semantic version which we increment each time we want to publish a new version of our package.
```
"main": "./src/lib/Counter.js",
"version": "1.0.51",
"files": [
    "src",
    "README.md"
],
"repository": {
    "type": "git",
    "url": "git+https://github.com/PrimeTimeTran/npm-counter"
},
```
Login to NPM from CLI, then publish it.

npm publish