Doc comments not recognized

[orome]

Only the first line of a documentation comment is recognized so that

• [ ] only the first line is highlight as a doc comment, while all subsequent lines are treated as regular comments; and
• [ ] doc comments are not collapsable.

[carymrobbins]

We might be able to do this by just updating the parsing lexer to consume the entire haddock as a single element instead of just the first line.