Add a record example using a typedef

[parlough]

A common use case I've already seen is to declare a typedef for a record.

It might be worth documenting a specific example where this makes sense in the typedef and/or the record documentation.

[RandalSchwartz]

Just be careful to emphasize that a typedef is an alias, not a new type.

typedef A = (int a1, String a2);
typedef B = (int b1, String b2);

final A aThing = (14, 'hello');
final B bThing = aThing; // this works!

This works of course because A and B are not really new types... just alias for the records. And records are the same type as long as they have the same shape.