Move round-robin ranking calculation to the manager

[Drarig29]

The viewer should not have much logic. It should just display data created by the manager.

So round-robin ranking calculation should go in the manager's get module. Just as the standings.

https://github.com/Drarig29/brackets-viewer.js/blob/5bdcdaa16b285694252412e6ad337bf630d08738/src/helpers.ts#L180-L193

Related: https://github.com/Drarig29/brackets-manager.js/issues/69 https://github.com/Drarig29/brackets-manager.js/issues/72