Add documentation for locale and timezone

[JMadgwick]

No description provided.

[cstes]

Instead of suggesting to use a configuration file named .dmrc in the user's home directory, why not suggest to use .profile or .xprofile in the user's home directory. I think that the file .dmrc is GNOME2 specific and is not used any longer in GNOME3 or GNOME45 but most of all , the file was meant to store the latest session, and is updated automatically (written to) by the display manager to store the last session. On the other hand the .profile or .xprofile in the user's home directory seem safer to set the LANG variable. The way I use it on OpenIndiana is to set LANG in my .profile and this is then automatically used by LightDM.

OpenIndiana specific (not default) script : https://github.com/OpenIndiana/oi-userland/blob/oi/hipster/components/desktop/lightdm/files/lightdm-session

It may be a good idea to document the lightdm-session script. (It is not a lightdm script, it is an OpenIndiana script).

[JMadgwick]

You're right that .dmrc is automatically created/updated. I've changed to make that clearer and also mention that LANG can be set in .profile and linked to that file. Using .profile would be most useful for terminal sessions, as naturally they won't read .dmrc.