feat(#2948): add custom decorators, :help nvim-tree-decorators (#2996)

* feat(#2948): add UserDecorator, proof of concept

* feat(#2948): add UserDecorator, proof of concept

* feat(#2948): add UserDecorator, proof of concept

* feat(#2948): add UserDecorator

* feat(#2948): add UserDecorator

* feat(#2948): add UserDecorator

* feat(#2948): add Decorator node icon override

* feat(#2948): add nvim_tree.api.* node classes

* feat(#2948): extract _meta following nvim pattern

* feat(#2948): extract _meta following nvim pattern

* feat(#2948): add decorator registry and order

* feat(#2948): add decorator registry and order

* feat(#2948): tidy

* feat(#2948): document API

* feat(#2948): document API

* feat(#2948): document API

* feat(#2948): pass api nodes to user decorators

* feat(#2948): document API

* feat(#2948): use renderer.decorators to define order and register

* feat(#2948): tidy decorator args and complete documentation

* feat(#2948): decorator classes specified by prefix rather than suffix

* feat(#2948): improve doc

* feat(#2948): improve doc

* feat(#2948): improve doc

* feat(#2948): additional user decorator safety

* feat(#2948): create nvim_tree.api.decorator.UserDecorator class in API, add :extend

* feat(#2948): improve doc

lua/nvim-tree/node/root.lua

@@ -22,4 +22,13 @@ function RootNode:destroy()
   DirectoryNode.destroy(self)
 end
 
+---Create a sanitized partial copy of a node, populating children recursively.
+---@param api_nodes table<number, nvim_tree.api.Node>? optional map of uids to api node to populate
+---@return nvim_tree.api.RootNode cloned
+function RootNode:clone(api_nodes)
+  local clone = DirectoryNode.clone(self, api_nodes) --[[@as nvim_tree.api.RootNode]]
+
+  return clone
+end
+
 return RootNode