X.L.Spacing: Extend documentation
X.L.Spacing: Extend documentation

Users are having trouble with this module all the time.  Now that
certain helper functions are undeprecated, we should tell users how they
may use them.  It is also worth explaining the scary-looking
`spacingRaw` command a bit further.

Related: https://github.com/xmonad/xmonad-contrib/pull/597

xmonad/xmonad-contrib,xmonad/xmonad-contrib