scripting.InjectionTarget.workers property to inject WorkerScope(s)

[hackademix]

Main world scripts should be able to modify JavaScript-accessible object (e.g. DOM prototypes or built-in functions) in a way that is transparent and cannot be subverted by page scripts., e.g. to modify or intercept the behavior of built-in objects for additional security, privacy and/or anti-fingerprinting reasons.

This requires them to be injected and running before site scripts in any scope, including WorkerScope(s) (otherwise these scope can be use to circumvent the main browsing context modifications).

I therefore propose to extend the scripting.InjectionTaget type with an optional workers property (boolean, default false) : if true, all the Worker and SharedWorker and ServiceWorker instances which are associated to the browsing contexts identified by this InjectionTarget object will be injected as well.

Parent issue: #103