Refer to the tutorial instead of X.D.Extending more often

Essentially, whenever the tutorial actually has decent material on the
subject matter.  The replacement is roughly done as follows:

  - logHook → tutorial
  - keybindings → tutorial, as this is thoroughly covered
  - manageHook → tutorial + X.D.Extending, as the manageHook stuff the
    tutorial talks about is a little bit of an afterthought.
  - X.D.Extending (on its own) → tutorial + X.D.Extending
  - layoutHook → tutorial + X.D.Extending, as the tutorial, while
    talking about layouts, doesn't necessarily have a huge focus there.
  - mouse bindings → leave this alone, as the tutorial does not at all
    talk about them.

XMonad/Actions/DynamicProjects.hs

@@ -113,7 +113,7 @@ import qualified XMonad.Util.ExtensibleState as XS
 -- >  , ((modm, xK_slash), shiftToProjectPrompt def)
 --
 -- For detailed instructions on editing your key bindings, see
--- "XMonad.Doc.Extending#Editing_key_bindings".
+-- <https://xmonad.org/TUTORIAL.html#customizing-xmonad the tutorial>.
 
 --------------------------------------------------------------------------------
 type ProjectName  = String