doc: explain what `npm outdated`' tells you
doc: explain what `npm outdated`' tells you

Fixes: #10687
Credit: da39a3ee5e6b4b0d3255bfef95601890afd80709@othiym23
Reviewed-By: da39a3ee5e6b4b0d3255bfef95601890afd80709@ashleygwilliams
PR-URL: https://github.com/npm/npm/pull/10695

evanlucas/npm,kemitchell/npm,evanlucas/npm,chadnickbok/npm,midniteio/npm,kimshinelove/naver-npm,misterbyrne/npm,lxe/npm,xalopp/npm,cchamberlain/npm-msys2,princeofdarkness76/npm,princeofdarkness76/npm,DaveEmmerson/npm,chadnickbok/npm,yibn2008/npm,evocateur/npm,evocateur/npm,ekmartin/npm,rsp/npm,misterbyrne/npm,TimeToogo/npm,lxe/npm,ekmartin/npm,yodeyer/npm,Volune/npm,rsp/npm,DIREKTSPEED-LTD/npm,evocateur/npm,Volune/npm,cchamberlain/npm,DaveEmmerson/npm,midniteio/npm,xalopp/npm,cchamberlain/npm-msys2,midniteio/npm,yibn2008/npm,cchamberlain/npm,kimshinelove/naver-npm,segrey/npm,kemitchell/npm,princeofdarkness76/npm,misterbyrne/npm,evanlucas/npm,rsp/npm,DaveEmmerson/npm,segrey/npm,cchamberlain/npm,yibn2008/npm,cchamberlain/npm-msys2,DIREKTSPEED-LTD/npm,yodeyer/npm,TimeToogo/npm,yodeyer/npm,DIREKTSPEED-LTD/npm,Volune/npm,segrey/npm,kimshinelove/naver-npm,TimeToogo/npm,kemitchell/npm,xalopp/npm,ekmartin/npm,lxe/npm,chadnickbok/npm