fix(#2024): revert removal of deprecated nvim-tree.config nvim_tree_callback

lua/nvim-tree/config.lua

@@ -0,0 +1,11 @@
+-- INFO: DEPRECATED FILE, DO NOT ADD ANYTHING IN THERE
+-- keeping to avoid breaking user configs. Will remove during a weekend.
+local M = {}
+
+-- TODO: remove this once the cb property is not supported in mappings, following view.mapping.list removal
+function M.nvim_tree_callback(callback_name)
+  -- generate_on_attach_.* will map this as per mappings.list..action
+  return callback_name
+end
+
+return M