[racket-dev] Tweaked doc pages

>> It's now available at newdocs.racket-lang.org.
>>
>> There are two things that need to be addressed:
>>
>> * The layout should have the main column centered.  (I thought that it
>>   was fine initially if the left column is part of the contents.)


The docs look good.  I'm a little confused at what looks like a
regression to PR 13305 though: when I look at the underscore-leading
identifiers of:

    http://newdocs.racket-lang.org/foreign/Other_Atomic_Types.html

both of them in the "On this page" are misrendered.  But when I look
at the page in my local HEAD-generated documentation, it's rendering
ok.  Do you know what's happening there?