bug#71048: The manual should have an example for treesit-language-at-point-function

[Eli Zaretskii]

> Date: Sun, 19 May 2024 02:00:23 +0300
> From: Dmitry Gutov <dmitry@gutov.dev>
> 
> https://www.gnu.org/software/emacs/manual/html_node/elisp/Multiple-Languages.html
>  
> has code examples for multiple-language setup (with tree-sitter modes), 
> and it more-or-less says that treesit-language-at-point-function should 
> be set.
> 
> But there is a default behavior for when it's not set, and the code 
> snippets in the second half of the page don't set it, so it seems prone 
> to mistakes.
> 
> I think the examples should include a setting for 
> treesit-language-at-point-function.
> 
> Inspired by https://github.com/dgutov/mmm-mode/issues/142

Yuan, could you please add such examples?