New comment by sgn on void-packages repository

https://github.com/void-linux/void-packages/pull/30549#issuecomment-844252689

Comment:
> @sgn it turns out `beancount` doesn't ship with its Emacs mode anymore. The elisp file is now in a separated repo at https://github.com/beancount/beancount-mode.
> 
> Should we make a notice message after the installation about this, in case it breaks someone's Emacs workflow?

I think we should package that separately and add a `README.voidlinux`. I think the consensus is NOT spam the `INSTALL.msg` for non-critical messages.