(renderer) TreeBuilder: add ipairs/pairs utilities

lua/u/renderer.lua

@@ -526,6 +526,26 @@ function TreeBuilder:nest(fn)
   return self
 end
 
+--- @param arr <T>[]
+--- @param f fun(tb: u.renderer.TreeBuilder, item: T, idx: number): any
+function TreeBuilder:ipairs(arr, f)
+  return self:nest(function(tb)
+    for idx, item in ipairs(arr) do
+      f(tb, item, idx)
+    end
+  end)
+end
+
+--- @param tab table
+--- @param f fun(tb: u.renderer.TreeBuilder, key: any, value: any): any
+function TreeBuilder:pairs(tab, f)
+  return self:nest(function(tb)
+    for k, v in pairs(tab) do
+      f(tb, k, v)
+    end
+  end)
+end
+
 --- @return u.renderer.Tree
 function TreeBuilder:tree() return self.nodes end
 -- }}}