bug#60305: Help with hideshow

[Yuan Fu]

Is anyone familiar with hideshow? I tried to add tree-sitter support for it but 
didn’t quite make it. 

I just generalized some defun functions so that one can define a “thing” with a 
regexp that matches node types. So now it should be relatively straightforward 
for each major mode to define a “block” thing, like they do for defun, and a 
hideshow-treesitter bridge can use treesit-thing-at-point, 
treesit-beginning-of-thing, etc, to support hideshow.

It would be great if someone familiar with hideshow would like to give it a 
try, or educate me how to set hs-special-modes-alist.

On the separate note, I wonder if the hideshow support can go on the release 
branch.

Thanks,
Yuan