fix: rotate Wit.ai API keys for English challenges

Closes #130.

src/background/main.js

@@ -15,6 +15,7 @@ import {
   functionInContext,
   getBrowser,
   getPlatform,
+  getRandomInt,
   arrayBufferToBase64
 } from 'utils/common';
 import {
@@ -220,7 +221,11 @@ async function prepareAudio(audio) {
 
 async function getWitSpeechApiKey(speechService, language) {
   if (speechService === 'witSpeechApiDemo') {
-    return witApiKeys[language];
+    if (language === 'english') {
+      return witApiKeys[language][getRandomInt(1, 4) - 1];
+    } else {
+      return witApiKeys[language];
+    }
   } else {
     const {witSpeechApiKeys: apiKeys} = await storage.get(
       'witSpeechApiKeys',

src/utils/config.js

@@ -8,7 +8,12 @@ const witApiKeys = {
   catalan: 'YBAZZV6ITGFD3C2QX7CANYQPMGUOI7RK',
   chinese: 'KBBALJMRKYDJJDMC4NJ32VWCBKFJFIIU',
   dutch: 'T43TEUNW4HDQFNUTIA3EYTTD4A22AS4H',
-  english: 'NVYD6ZUJMC26US5XS2ZJJ32EDZZ654TD',
+  english: [
+    'BQE4QJJNYC6JVTDULHYIZHQOQFWUVDCQ',
+    'EQAXGAJVZIMI3YMILN2XQZY7IWGUPKGL',
+    'AA3LFNYPDNXX4MUDQQJNLT74YFRQ3M6F',
+    'DRTXENV66YE44PRYOJGWPX2BPGZNPYTQ'
+  ],
   finnish: '3GOWLMYD7DUY72XTPJW6QTVZSK2QEAPT',
   french: 'JLNITTO2D4KMEOGQ6MTSN634ADK62VZ7',
   german: 'LPVVXWRBFTVBOOHZAEJC3QRM6E3UMD7I',