Scopes: what is GeneratedRange.isScope?

[connor4312]

It's missing jsdocs and I don't see it referenced in text/issues anywhere, was curious 🙂

[szuend]

Initially this was planned to mark generated ranges that are actual JS scopes in the generated code (opposed to e.g. an inlined function body). But it turned out that debuggers don't really need this info.

I propose a change with #114 where we re-use the flag to mean "this generated range is a function/arrow function/constructor in the generated code (aka it can be called)". This would allow stack trace processors to effectively determine whether a stack frame can be omitted or not.