Fix most npm vulnerabilities

There are a few npm warnings remaining but they rely on other packages to update like React:
facebook/create-react-app#11054

For now, I've switched the build to use Yarn which allows us to use resolutions to include the newer versions of these insecure packages.

The end result is that npm will still say there are fixes required, but the actual packages being used to build this package are the fixed versions.

Author: Curtis Cummings

LICENSE

@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2020 Aquil.io
+Copyright (c) 2021 Simple File Upload
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

README.md

@@ -4,7 +4,7 @@
 
 [![NPM](https://img.shields.io/npm/v/react-simple-file-upload.svg)](https://www.npmjs.com/package/react-simple-file-upload) [![JavaScript Style Guide](https://img.shields.io/badge/code_style-standard-brightgreen.svg)](https://standardjs.com)
 
-Simple File Upload is currently invite only. If you want to test it out, please reach out to [Colleen Schnettler](https://twitter.com/leenyburger) for an API Key.
+Get an API key by signing up at [Simple File Upload](https://www.simplefileupload.com/).
 
 ## Install
 
@@ -28,4 +28,4 @@ const File Editor = () => (
 
 ## License
 
-MIT © [Pixelplicity](https://github.com/pixelplicity)
+MIT © [Simple File Upload](https://www.simplefileupload.com)