Misuse of `Reference` and other transferable APIs may lead to access to nodejs isolate

Versions of isolated-vm before v4.0.0, and especially before v3.0.0, have API pitfalls which may make it easy for implementers to expose supposed secure isolates to the permissions of the main nodejs isolate.

Reference objects allow access to the underlying reference's full prototype chain. In an environment where the implementer has exposed a Reference instance to an attacker they would be able to use it to acquire a Reference to the nodejs context's Function object.

Similar application-specific attacks could be possible by modifying the local prototype of other API objects.

Access to NativeModule objects could allow an attacker to load and run native code from anywhere on the filesystem. If combined with, for example, a file upload API this would allow for arbitrary code execution.

To address these issues the following changes were made in v4.0.0:

• Documentation was updated with more explicit guidelines on building secure applications.
• Reference instances will no longer follow prototype chains by default, nor will they invoke accessors or proxies.
• All isolated-vm API prototypes are now immutable.
• NativeModule constructor may only be invoked from a nodejs isolate.