Allow `this` to be part of the qualified name.

[Andarist]

If I read things correctly - this is not allowed because QualifiedName only allows Identifiers and those don't allow reserved words: https://tc39.es/ecma262/multipage/ecmascript-language-expressions.html#prod-Identifier

It would be cool if this.X could be used as an extractor object. A wrapper object/class might accept another that is responsible for maintaining a state that otherwise is opaque to the wrapper itself and it would be very nice if the extraction concerns could be delegated to that inner object.

[rbuckton]

This will be addressed by #12.

[Jack-Works]

do I need to make any changes to the pattern-matching site?

[rbuckton]

No, I believe the definitions I'm using in the current spec text are essentially the same as the ones used in pattern matching.