[Feature]: Support live transaction streaming of beacon chain summary

[ghost]

The BeaconChain's explorer should support a feature to stream the transactions submitted to the beacon summary in near real time.

The idea would be to create processes responsible for creating asynchronous communication with the pool of storage node for the next summary. Those nodes will notify clients about new transaction arrived (note: this approach will be less intensive than a polling mechanism).

Each Beacon's subset can have a list of subscribers for summary updates

The feature should support the switch of pool when there is a new summary timer event. (pools may change for every interval).

When those processes received a notification of new transaction, they will submit a message through PubSub to update the UI elements.