refactor(#3256): move setup/config related functionality to new module config.lua (#3262)

* refactor(#3253): move setup/config related functionality to new module config.lua

* refactor(#3253): add api.config, tidy new config module

* refactor(#3253): add api.config, tidy new config module

* refactor(#3253): add api.config, tidy new config module

* refactor(#3253): format

* refactor(#3256): fix doc generator

* refactor(#3256): fix doc generator

* refactor(#3256): strongly type legacy config

* refactor(#3256): legacy config consistent parameter naming

* refactor(#3256): fix bad rebase

Author: alex-courtis

CONTRIBUTING.md

@@ -161,7 +161,7 @@ Please add or update documentation when you make changes, see `:help dev-lua-doc
 
 Help is updated for:
 - Default keymap at `keymap.on_attach_default`
-- Default config at `--- default-config-start`
+- Default config at `--- config-default-start`
 
 ## Updating And Generating
 

doc/nvim-tree-lua.txt

@@ -2385,6 +2385,28 @@ get()                                           *nvim_tree.api.commands.get()*
         • {opts} (`vim.api.keyset.user_command`) |command-attributes|
 
 
+==============================================================================
+API: config                                             *nvim-tree-api-config*
+
+default()                                     *nvim_tree.api.config.default()*
+    Default nvim-tree config.
+
+    Return: ~
+        (`nvim_tree.config`) immutable deep clone
+
+global()                                       *nvim_tree.api.config.global()*
+    Global current nvim-tree config.
+
+    Return: ~
+        (`nvim_tree.config`) immutable deep clone
+
+user()                                           *nvim_tree.api.config.user()*
+    Reference to config passed to |nvim-tree-setup|
+
+    Return: ~
+        (`nvim_tree.config?`) nil when no config passed to setup
+
+
 ==============================================================================
 API: events                                             *nvim-tree-api-events*