message: Adds an Open Collective donate button to the readme
diff: @@ -15,7 +15,13 @@ If you want to keep up to date with the latest PixiJS news then feel free to fol
  and we will keep you posted! You can also check back on [our site](http://www.pixijs.com)
  as any breakthroughs will be posted up there too!
  -**Your support helps us make PixiJS even better. Make your pledge on [Patreon](https://www.patreon.com/user?u=2384552&ty=h&u=2384552) and we'll love you forever!**
  +**We are now a part of the [Open Collective](https://opencollective.com/pixijs) and with your support you can help us make PixiJS even better. To make a donation, simply click the button below and we'll love you forever!**
  +
  +<div align="center">
  + <a href="https://opencollective.com/pixijs/donate" target="_blank">
  + <img src="https://opencollective.com/pixijs/donate/button@2x.png?color=blue" width=250 />
  + </a>
  +</div>
  ### What to Use PixiJS for and When to Use It
  