title: Mobx does not see changes done inside setInterval
body: <p>I have a screen like that</p>
  <pre><code>const ScreenA = observer(() =&gt; {
    const { userStore } = useRootStore();
  
    useEffect(() =&gt; {
      setInterval(() =&gt; {
        userStore.ping();
      }, 3000);
    }, []);
  
    console.log(userStore.pingResult);
  
    retunr &lt;&gt;&lt;/&gt;
  });
  </code></pre>
  <p>And store</p>
  <pre><code>class UserStore {
    pingResult = null;
  
    ping = async () =&gt; {
      console.log('ping');
      const pingResult = await this.userService.ping();
      runInAction(() =&gt; {
        this.pingResult = pingResult;
      });
    };
  }
  </code></pre>
  <p>The problem is <code>console.log(userStore.pingResult);</code> works only once — I guess, observer just can't see that store has been updated. Tried to JSON.parse(JSON.stringify(pingResult)) to make sure that pingResult is completely new, but it didn't work. At the same time <code>console.log('ping')</code> works as expected — every 3 seconds.</p>