Feature request - Warm up build environment to accept multiple build requests

[danvim]

Is it possible to pre-launch the headless browser to anticipate multiple later CLI calls to build outputs so it reduces the overhead in launching the browser/preparing the environment?

[spring-raining]

We also received a request in #560 to build output on demand on request. Currently, it is possible to run this in a separate process using child_process by request, but we recognize that this is not the best approach for performance.