Allow specification of `override`

[listrophy]

There is probably a compiler error in this situation:

class Parent {
    var description: String { "Some description" }
}

@Inscribe class Child: Parent {} // compiler error

Allow an (override: true) parameter:

class Parent {
    var description: String { "Some description" }
}

@Inscribe(override: true) class Child: Parent {}
// expands to:
class Child: Parent {}
extension Child {
    override var description: String { "Child" }
    override static var description: String { "Child" }