docs(treesitter): document TSNode:named_children()

This commit also gives an internal documentation description for
`TSNode:__has_ancestor()`.

runtime/doc/treesitter.txt

@@ -804,6 +804,12 @@ TSNode:named_child_count()                        *TSNode:named_child_count()*
     Return: ~
         (`integer`)
 
+TSNode:named_children()                              *TSNode:named_children()*
+    Returns a list of the node's named children.
+
+    Return: ~
+        (`TSNode[]`)
+
                                          *TSNode:named_descendant_for_range()*
 TSNode:named_descendant_for_range({start_row}, {start_col}, {end_row},
                                   {end_col})

runtime/lua/vim/treesitter/_meta/tsnode.lua

@@ -10,8 +10,6 @@ error('Cannot require a meta file')
 
 ---@nodoc
 ---@class TSNode: userdata
----@field named_children fun(self: TSNode): TSNode[]
----@field __has_ancestor fun(self: TSNode, node_types: string[]): boolean
 local TSNode = {} -- luacheck: no unused
 
 --- Get the node's immediate parent.
@@ -62,6 +60,15 @@ function TSNode:child(index) end
 --- @return integer
 function TSNode:named_child_count() end
 
+--- Returns a list of the node's named children.
+--- @return TSNode[]
+function TSNode:named_children() end
+
+--- Check if the node has any of the given node types as its ancestor.
+--- @param node_types string[]
+--- @return boolean
+function TSNode:__has_ancestor(node_types) end
+
 --- Get the node's named child at the given {index}, where zero represents the
 --- first named child.
 --- @param index integer