Sample: Update minimizable sample with multiple polling interval

This sample work should not touch the production code of Web Chat. If modifying Web Chat is needed to complete this sample, by either accomplishing the objective, or making the sample code more intuitive and easy to understand. Please discuss before modifying the production code.

In our sample 12, "minimizable UI", the Web Chat UI is initially minimized. In this early minimized state, Web Chat will not connect to Direct Line channel.

After the UI is restored, Web Chat will start to connect to Web Chat. And for subsequent minimizes, the Direct Line channel will remain active/connected.

Since polling interval on DirectLineJS can be tweaked (for RESTful connection), it will be great to explore this feature:

• On subsequent minimize, (a.k.a. connected to Direct Line), the hosting page can reconfigure DirectLineJS to use a less aggressive timing for polling interval (default is 1s)
• On subsequent restore, the hosting page will reconfigure the polling interval back to default value

Please verify in network trace that the polling interval settings work. If not, please file a bug to DirectLineJS repository and link it here.

Start with sample 12, “minimizable UI,” and review how it creates or configures the DirectLineJS connection when the UI is minimized and restored. Explore DirectLineJS polling interval configuration, then verify the changed intervals in a network trace; if they do not work, file and link a DirectLineJS bug as requested.