docs: add a new command boilerplate code

Having howtos is good, having an working code that can be used as-is to
kickstart a write of a new command is better.

Signed-off-by: Sami Kerola <kerolasa@iki.fi>
build-sys: unify function and variable attribute spacing

From two different styles the more popular is picked to be the correct
way for this package.

$ git grep -hc '__ ((__' | awk -F: '{T+=$2} END  {print T}'
144
$ git grep -hc '__((__'  | awk -F: '{T+=$2} END  {print T}'
163

Signed-off-by: Sami Kerola <kerolasa@iki.fi>