fix: avoid request ISSUE been cached

relate gitalk#96

Author: booxood

src/gitalk.jsx

@@ -190,7 +190,8 @@ class GitalkComponent extends Component {
  params: {
  client_id: clientID,
  client_secret: clientSecret,
- labels: labels.concat(id).join(',')
+ labels: labels.concat(id).join(','),
+ t: Date.now()
  }
  }).then(res => {
  const { admin, createIssueManually } = this.options