[dev] Reflect channel change in URL

It means that if I go to a channel and refresh the page, I will be
reconnected to this channel after refresh.

app/index.js

@@ -784,6 +784,11 @@ class GlobalBindings {
     this.requestMove = (user, channel) => {
       if (this.connected()) {
         user.model.setChannel(channel.model)
+        // reflect this change in URL
+        let currentUrl = url.parse(document.location.href, true)
+        currentUrl.query.channelName = channel.name()
+        delete currentUrl.search
+        window.history.pushState(null, channel.name(), url.format(currentUrl))
       }
     }