bug#60894: 30.0.50; [PATCH] Add treesit-forward-sexp

[Stefan Monnier]

> backward-up-list might even work automatically with a sufficiently
>  conforming forward-sexp-function (it does with SMIE);

I'm happy to hear that opinion, but it's a bit too optimistic:
`backward-up-list` doesn't really work sufficiently well (IMO) just
using `forward-sexp-function`.

My SMIE experience with it is that we really need a specific hook
for that if we want to avoid wonky behaviors in "corner" cases.


        Stefan