Minor user guide fixes

[Vilius Panevėžys]

Hi Mikolaj,
thank you for the prompt reply!

On Sat, 28 May 2022 17:10:24 +0200
Mikolaj Konarski <mikolaj at well-typed.com> wrote:

> Would you like to create a pull request on github with these changes
> to help us see them in context, e.g., whether they merge cleanly and
> which branch, and to help us credit you properly?

I don't use GitHub, so I hope it's not too much trouble to just `git
am` the patches. I've rebased the patches on master today, so they
should apply cleanly. However, if it turns out you need me to make any
revision - let me know.

My appreciation goes to all the people who have put in the time and
effort into creating the user guide (not to mention Cabal itself!).