message: Update README.md
  Capitalization typo
diff: @@ -182,7 +182,7 @@ const newXeroClient = new XeroClient()
  const refreshedTokenSet = await newXeroClient.refreshWithRefreshToken(client_id, client_secret, tokenSet.refresh_token)
  ```
  -Making AUthorized API calls:
  +Making Authorized API calls:
  ```js
  const tokenSet = getTokenSetFromDatabase(userId) // example function name
  