Add websocket "ping" handler

[yuvenus]

Adding a websocket "ping" handler to WebsocketNetworkConnection to send pongs back with the same incoming payload.

This merges into rc-1.2.0 because I'm not certain what release this will be a part of; please let me know if I need to retarget!

I tested this locally with a quick node.js script to open a websocket connection and am properly receiving pongs from a locally running Citrine instance.

Local code sample

const { WebSocket } = require('ws');

main = () => {
    console.log('opening websocket to citrine');
    const ws = new WebSocket('ws://localhost:8081/Charger2', 'ocpp2.0.1');

    ws.onopen = () => {
        console.log('sending boot notification');
        var BN = JSON.stringify([2, '1231231231231231', 'BootNotification', {
            'chargingStation': {
                'vendorName': 'local',
                'model': 'localCharger',
                'serialNumber': 'CHARGER02'
            },
            'reason': 'PowerUp'
        }]);
    
        ws.send(BN);
    
        console.log('pinging');
        ws.ping('hello!');
    }    

    ws.on('pong', (data) => {
        console.log(`received pong with data ${JSON.stringify(data)} -- closing websocket now`);
        ws.close();
    });
}

main();

Resulting local logs from ping/pong

• opening websocket to citrine
• sending boot notification
• pinging
• received pong with data {"type":"Buffer","data":[104,101,108,108,111,33]} -- closing websocket now

Resulting Citrine logs from ping/pong

2024-05-07 14:46:43 2024-05-07 18:46:43.155 DEBUG /usr/local/apps/citrineos/02_Util/dist/networkconnection/WebsocketNetworkConnection.js:308 CitrineOS Logger:WebsocketNetworkConnection Ping received for Charger02 with message {"type":"Buffer","data":[104,101,108,108,111,33]}