doc: clarify open/toggle defaults, more robust legacy argument handling

lua/nvim-tree/api.lua

@@ -18,16 +18,16 @@ end
 
 ---@class ApiTreeOpenOpts
 ---@field path string|nil path
----@field current_window boolean|nil
+---@field current_window boolean|nil default false
 
 Api.tree.open = require("nvim-tree").open
 
 ---@class ApiTreeToggleOpts
 ---@field path string|nil
----@field current_window boolean|nil
----@field focus boolean|nil
----@field find_file boolean|nil
----@field update_root boolean|nil
+---@field current_window boolean|nil default false
+---@field focus boolean|nil default true
+---@field find_file boolean|nil default false
+---@field update_root boolean|nil default false
 
 Api.tree.toggle = require("nvim-tree").toggle