a brace-based indenting patch

[Sašo Živanović]

Hi all!

Sorry for bothering the mailing list with this, but I'm new at Savannah 
and I'm not sure how to propose a patch.

I have generalized the brace-based indenting to support arbitrary 
delimiters (like "[]" or "()"). I have been using this for a while 
myself, and it has recently been asked for at TeX.SE 
(https://tex.stackexchange.com/q/635747/16819), for indentation of 
Forest trees (something I care about, as I'm the author of Forest).

I kindly ask you to let me know how I can make a contribution to the 
project. I'm not really good at Lisp, so I'm not sure I should be a 
project member. If all there's needed is the patch that some project 
member can pull in, I have uploaded that to my nextcloud: 
https://spj.ff.uni-lj.si/nextcloud/s/MJ3skPaQkQfpLYR/download

Best,
Sašo Živanović