feat(starter-game-template): Add ability to listen to transaction receipts from Nakama

[jerargus]

Implement a mechanism for client to subscribe to transaction receipts.

A single match is created inside of Nakama. Clients can join the match. All transaction receipts will be pushed to all members of the match.

Transactions are fetched from Cardinal in a background process. If no clients are listening to transaction receipts (i.e. no clients have joined the match), transaction receipts will be dropped on the floor.

Also in this PR is a barebones js client that will listen for transaction receipts and print them to the screen.

Problems with this implementation:

1. All receipts are sent to all clients. Ideally, clients will only receive transactions that they initiated.
2. There is only 1 match. It's not clear what performance bottlenecks we'll encounter when a large number of players join that singleton match. Ideally matches will be dynamically created as clients subscribe and unsubscribe to transaction receipts.
3. Nakama's documentation warns against sending too much data too frequently (https://heroiclabs.com/docs/nakama/concepts/multiplayer/authoritative/#send-data-messages) -- tl;dr: They want implements to limit broadcasted messages to 1000 bytes per message and 1 message per client per tick (This is a Nakama tick, not a Cardinal tick).

Testing PR can be done by:

1. running Cardinal/Nakama normally with mage start
2. running npm install the node main.js from the jsclient directory
3. sending transactions to Nakama via the API Explorer.

[technicallyty]

utACK