docs(readme): add discord badge

Author: jpoehnelt

README.md

@@ -6,6 +6,7 @@
 [![codecov](https://codecov.io/gh/googlemaps/js-api-loader/branch/master/graph/badge.svg)](https://codecov.io/gh/googlemaps/js-api-loader)
 ![GitHub contributors](https://img.shields.io/github/contributors/googlemaps/js-api-loader?color=green)
 [![semantic-release](https://img.shields.io/badge/%20%20%F0%9F%93%A6%F0%9F%9A%80-semantic--release-e10079.svg)](https://github.com/semantic-release/semantic-release)
+[![Discord](https://img.shields.io/discord/676948200904589322?color=6A7EC2&logo=discord&logoColor=ffffff)](https://discord.gg/jRteCzP)
 
 ## Description
 Load the Google Maps JavaScript API script dynamically. This takes inspiration from the [google-maps](https://www.npmjs.com/package/google-maps) npm package but updates it with ES6, Promises, and TypeScript.