Fetch measure. in real-time

[BECATRUE]

Feature you want to implement

I will implement a feature to fetch measurement of a specific channel in real-time.

How the feature is implemented

This would be implemented using WebSocket, like #6.

Also, to prevent measurements from accumulating excessively, data older than 10 minutes will be deleted every 10 minutes using setInterval().

Additional context

It is communicated with the WebSocket implemented in snu-quiqcl/wlm-server#18.