Treat literals as special cases when parsing

[Rich-Harris]

Alternative to #426

[Conduitry]

This seems reasonable - but the literals should probably be a map, not an object, otherwise anything in Object.prototype would also be seen as a literal. Because of the all-lowercase regex check, I guess all that would affect is {{constructor}}, which would always be interpreted as a literal equal to Object.prototype.constructor, instead of (possibly) whatever other value it should.

[Rich-Harris]

Good point! I always forget that I can use Map. Old habits.

[Conduitry]

LGTM 👍