setup(): Add section to help pages

Author: mizlan

doc/nnn.txt

@@ -185,6 +185,18 @@ g:nnn#shell                                                      *g:nnn#shell*
                   Default: &shell
                   The shell to run the terminal window.
 
+require('nnn').setup{}                                          *nnn-lua-setup*
+                  Default: same as Vimscript defaults
+                  An alternative way to configure n³ more suitable for
+                  init.lua users. For example:
+>
+                  require('nnn').setup{
+                      set_default_mappings = false,
+                      session = 'global',
+                      layout = { left = '20%' }
+                  }
+<
+
 
 -----------------------------------------------------------------------------
 Functions                                                            *nnn-func*