Better support for inline examples with type signatures

[pchiusano]

So this works right now, allowing you to have hyperlinked type expressions inline in a Doc:

x = {{
  For example, given {{ docExample 1 '(x -> x : Map Nat Text) }}, blah blah blah.

This will render as x : Map Nat Text with the type annotation being clickable. Unfortunately, this trick only works if the annotation uses no type variables.

What should work:

somedoc = {{
  For instance in {{ docExample 1 '((x -> x) : forall a b . Map a b -> Map a b }}, 
  returns blah blah blah. 

And this could render as x : Map a b, I think with a minor tweak to the doc renderer.

Currently it renders as

(x -> x) : (∀ k v. Map k v -> Map k v)`

My proposed rule is that if the thing being rendered is a lambda with an annotation, and the first parameter of the lambda is being elided for display, move the thing to the right of the -> type arrow in as an annotation.

This could also use some better syntax than having to transclude out to docExample