Document the eglfs-specific loadKeymap

Change-Id: I617c66602a0e3b7a65d9bf0afc72a6ba4d3cc2ee
Reviewed-by: Risto Avila <risto.avila@theqtcompany.com>
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>