[LyX/master] French manual Customization.lyx : import from 2.3

[jpc]

commit 6b508e959c05d5324006afc05f744a487f1b05c1
Author: jpc <jpc at lyx.org>
Date:   Thu Aug 20 17:14:06 2020 +0200

                French manual Customization.lyx : import from 2.3

 lib/doc/fr/Customization.lyx | 1386 ++++++++++++++++++------------------------
 1 files changed, 590 insertions(+), 796 deletions(-)