feat(#2948): add UserDecorator

lua/nvim-tree/renderer/builder.lua

@@ -16,11 +16,6 @@ local DecoratorOpened = require("nvim-tree.renderer.decorator.opened")
 
 local pad = require("nvim-tree.renderer.components.padding")
 
----TODO move all these classes to API meta
----@class (exact) HighlightedString
----@field str string
----@field hl string[]
-
 ---@class (exact) AddHighlightArgs
 ---@field group string[]
 ---@field line number

lua/nvim-tree/renderer/decorator/meta.lua

@@ -11,3 +11,8 @@
 ---@field enabled boolean
 ---@field highlight_range DecoratorHighlightRange
 ---@field icon_placement DecoratorIconPlacement
+
+---A string for rendering, with optional highlight groups to apply to it
+---@class (exact) HighlightedString
+---@field str string
+---@field hl string[]

lua/nvim-tree/renderer/decorator/user.lua

@@ -2,15 +2,15 @@ local Decorator = require("nvim-tree.renderer.decorator")
 
 ---Abstract user decorator, extend to define your own.
 ---Icon and highlight are optional.
----Constructor will be called once per tree render, with no arguments:
+---Mandatory constructor will be called once per tree render, with no arguments:
 ---  Must call super passing DecoratorArgs: MyDecorator.super.new(self, args)
 ---  Must call define_sign, when using "signcolumn"
 ---See example at end.
 
 ---@class (exact) UserDecorator: Decorator
 local UserDecorator = Decorator:extend()
 
----Override this method to provide icons and the highlight groups to apply to them
+---Override this method to provide icons and the highlight groups to apply to DecoratorIconPlacement
 ---@param node Node
 ---@return HighlightedString[]? icons
 function UserDecorator:calculate_icons(node)