Fix []() .vimrc replacement

[rwxrob]

Rather than have any []() detected and replaced with a DDG search I'd
like to have it automatically filter it out and add it to the bottom of
the file with the rest of the referral links. (Ironically, I once had
this working.) In fact, all the [foo] stuff should automatically be
filtered and added to the bottom if not found so I just have to fill in
the links and not forget about them.