Please allow Javascript 'eval' functionality

[brr53]

I understand that 'eval' is disabled due to security concern.
However, please consider allowing the developer to decide if he/she wants to enable eval.

'Eval' is very useful in many NodeJS applications. I suggest perhaps just displaying a warning to developers who want to use eval instead of completely blocking the feature.

[jasnell]

For the production environment enabling eval, even optionally, runs the risk of security issues for the entire platform and not just the one worker. For local dev using workerd only, we do now have the UnsafeEval binding type that you can use (e.g. env.unsafe.eval('...') and env.unsafe.newFunction(...). There's a sample worker that shows how to use it.