Fix prerender

[alberto98fx]

This PR is an attempt to bring the pre-render to a semi stable state where we get no more 504

[alberto98fx]

For some reasons our code is not able to spawn chromium at startup so I had to make it a child process, the code is async that means chromium might take a while to be ready but prerender will keep retrying to connect.

[alberto98fx]

The setTimeout is commented out because of this error:

/home/node/node_modules/ws/lib/WebSocket.js:359
      if (cb) cb(new Error('not opened'));
                 ^

Error: not opened
    at WebSocket.send (/home/node/node_modules/ws/lib/WebSocket.js:359:18)
    at Chrome.enqueueCommand (/home/node/node_modules/chrome-remote-interface/lib/chrome.js:130:16)
    at /home/node/node_modules/chrome-remote-interface/lib/chrome.js:88:28
    at new Promise (<anonymous>)
    at Chrome.send (/home/node/node_modules/chrome-remote-interface/lib/chrome.js:87:16)
    at Object.handler [as continueInterceptedRequest] (/home/node/node_modules/chrome-remote-interface/lib/api.js:32:23)
    at Chrome.<anonymous> (/home/node/lib/plugins/blockResources.js:62:30)
    at Chrome.emit (node:events:513:28)
    at Chrome.handleMessage (/home/node/node_modules/chrome-remote-interface/lib/chrome.js:311:16)
    at WebSocket.<anonymous> (/home/node/node_modules/chrome-remote-interface/lib/chrome.js:274:27)```