add event handler for frontend

[clifforum]

because we dont have visibility on FE side flow for the purview FE.
I added this events system, so in the orum code, we could add listeners to the different events and log metrics accordingly.

Basically so we could track the connection attempts, failures and successes.

In orum code we will need to add custom js code that will listen to events like this:

window.addEventListener('purview', (e: CustomEvent) => {
  const event = e.detail as PurviewEvent;
  switch(event.type) {
    case 'websocket:open':
      console.log('WebSocket open');
      break;
    case 'websocket:error':
      console.log('error', event.detail);
      break;
   case 'websocket:close':
      console.log('closed', event.detail);
      break;
  }
});

[denpoly-orum]

I'd also consider adding a log event here too, so we have a record of the refresh 😎