[bug#36311] doc: Add subsection and note about environment variables.

[Nicolas Goaziou <mail@nicolasgoaziou.fr>]

Hello,

swedebugia <swedebugia@riseup.net> writes:

>> +Following the installation we recommend putting all environment variables into
>> + @file{~.bash_profile} to make sure they are only executed when your login to
>> + a shell (ie. open up a virtual terminal).

I think @file{~/.bash_profile} is clearer.

Also "ie. open up…" -> "i.e., open up…" or "i.e.@: open up…"

>> +If you use bash and put them into @file{.bashrc} you will end up with errors
>> +because this file is executed by bash EVERY time a new environment is entered

Maybe @emph{every}, since emphasizing with capitals is typographically
suboptimal.

>> +(e.g. when entering a pure environment with @command{guix environment guix
>> +--pure} and contaminate the environment).

"e.g. when" -> "e.g., when" or "e.g.@: when". 

See (info "Not Ending a Sentence") for more information.

Also, according to (info "@command"), it shoud be either @samp or @code.
After a cursory look, "guix.texi" seems to use "@code" for entire shell
command invocations.

HTH,

-- 
Nicolas Goaziou