Add WebSocket to eslint globals (#27044)

Summary:
WebSocket is giving an error by eslint. ('WebSocket is not defined').

[websocket-support](https://facebook.github.io/react-native/docs/network#websocket-support)

## Changelog
[General] [Fixed] - Add WebSocket to eslint globals
Pull Request resolved: #27044

Test Plan: Run eslint on a react native project using WebSocket. Eslint verification should pass.

Differential Revision: D18223891

Pulled By: cpojer

fbshipit-source-id: c4adfde07078133930aa0ed80be5615d128f4148

packages/eslint-config-react-native-community/index.js

@@ -106,6 +106,7 @@ module.exports = {
     setImmediate: true,
     setInterval: false,
     setTimeout: false,
+    WebSocket: true,
     window: false,
     XMLHttpRequest: false,
   },