LU-18890 doc: add "lfs find -ls" option to lfs-find.1 man page

LU-18890 doc: add "lfs find -ls" option to lfs-find.1 man page

The "lfs find -ls" option added in LU-15504 was not
documented in the lustre/doc/lfs-find.1 man page. This
patch adds proper documentation for this option, including:

- Adding the option to the SYNOPSIS section
- Adding a detailed description in the OPTIONS section
- Adding an example showing how to use the option

Fixes: 1d8164fa ("LU-15504 utils: lfs find -ls function")

Test-Parameters: trivial
Signed-off-by: Patrick Farrell <pfarrell@whamcloud.com>
Change-Id: Iecdc99d490f840c9beea62fb3b2c0bf49031b08c
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/58688
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Timothy Day <timday@amazon.com>
Reviewed-by: Frederick Dilger <fdilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>