make linking of default groups for tree style and add docs

doc/nvim-tree-lua.txt

@@ -134,6 +134,8 @@ Mouse support defined in |KeyBindings|
 ==============================================================================
 HIGHLIGHT GROUPS				        *nvim-tree-highlight*
 
+|lua_tree_highlight|				        *lua_tree_highlight*
+
 All the following highlight groups can be configured by hand. It is not
 advised to colorize the background of these groups.
 
@@ -175,5 +177,13 @@ LuaTreeGitMerge
 LuaTreeGitRenamed 
 LuaTreeGitNew 
 
+There are also links to normal bindings to style the tree itself.
+
+Normal
+EndOfBuffer
+CursorLine
+VertSplit
+CursorColumn
+
  vim:tw=78:ts=8:noet:ft=help:norl:
 

doc/tags

@@ -8,6 +8,7 @@ g:lua_tree_ignore	nvim-tree-lua.txt	/*g:lua_tree_ignore*
 g:lua_tree_show_icons	nvim-tree-lua.txt	/*g:lua_tree_show_icons*
 g:lua_tree_side	nvim-tree-lua.txt	/*g:lua_tree_side*
 g:lua_tree_size	nvim-tree-lua.txt	/*g:lua_tree_size*
+lua_tree_highlight	nvim-tree-lua.txt	/*lua_tree_highlight*
 nvim-tree-commands	nvim-tree-lua.txt	/*nvim-tree-commands*
 nvim-tree-features	nvim-tree-lua.txt	/*nvim-tree-features*
 nvim-tree-highlight	nvim-tree-lua.txt	/*nvim-tree-highlight*