Minor user guide fixes

[Mikolaj Konarski]

Hi Vilius,

> I did not know a PR is required.

It is. PRs automate a lot of things. Ci is run,
reviews are collected, including comments to specific
lines, and responded to via text and via code and marked
as done. The patch is automatically rebased and merged.
Backports are created, etc., etc.,

> I presumed patches via email are
> acceptable as they often are in projects that use mailing lists,
> especially a -devel list.

I think the disconnect is that today very few of cabal developers
are on this mailing list and there is very little traffic so you can't
expect a dev discussion on the list or a crowd of helpful devs
to share the chores. We should probably close the list
to avoid such misunderstandings. However, in case
github/gitlab/etc. break down, are censored, cancelled and/or betray
their social mandate, we have a low-tech and open alternative,
which was proven to work adequately in the Stone Age, so should
work in the post-apocalypse as well. However, I'd rather use
non-stone tools for as long as possible.

Cheers,
Mikolaj