fix: multiline JSX string conversion to string

[marvinhagemeister]

You learn something new every day! Turns out that contrary to standard JS string literals, JSX strings are allowed to span multiple lines.

<Foo
  description="Register a module with the third party
      registry."
/>

When we convert that to a jsx() call and the values to standard string literals we need to account for this and normalize them back to a valid JS strings.

jsx(Foo, { description="Register a module with the third party registry." });

[dsherret]

LGTM!