[Documentation] linux installation suggestions

On the installation's entry for linux it (very helpfully) suggest that if you want formated manpages on hover you can download rmarkdown and pandoc (which comes preinstalled with r-studio). For those who do not have R studio they'd be surprised to learn that pandoc depends on haskell, and thus the base package and it's dependencies can weigh up to 500mbs. I think it's a bit silly to suggest a large package just for syntax highlighting on function manpage tooltips (something which has native and less heavy alernatives on linux), but I also think the observation is relevant for those who might wonder why their mangpages are in plain text.

I think this can be edited to be part of the installation but not in the order of the default installation steps, but rather a suggestion or a note somewhere else in the doc. I can do this as the pages are editable but I'd like to know if it's ok first!

I believe the changes were made by @18kimn

Open the Installation: Linux wiki page linked in the issue and review where rmarkdown and pandoc are presented in the default installation steps. Move or reframe that guidance as an optional suggestion or note, including the potential dependency size; done means Linux users can distinguish the optional formatted-manpage setup from the default installation.