Add Type Alias and Fix Record Type Translation in ts2mls

[NeilKleistGao]

Related Issue: #134

[NeilKleistGao]

I think we may separate namespace and alias from class and trait parsing(case (KEYWORD(k @ ("class" | "trait" | "type" | "namespace")), l0) :: c), because their syntax should be different. e.g. a namesapce should not have a parent namespace. 🤔

[LPTK]

I find it's better to be very lax and do semantic validation afterwards, because parsing errors are usually worse than semantic errors.

[NeilKleistGao]

OK! And to keep NewParser.scala unchanged, I genetate type alias like this type Option: (None) | (Some<A>). Is this syntax acceptable?

[LPTK]

Not really no, we need = here. It's fine to extend NewParser.scala for that. But it should check that = is used for aliases and : for classes.

[NeilKleistGao]

Also fixed a typo getTypeParametes.

[LPTK]

Otherwise LGTM!

[LPTK]

After addressing the comments don't forget to use "squash and merge" and clean up the commit message.