slock.1: improve man page

* Fix all lint warnings.
* Remove "Op Ar arg..." in the description. It looks ugly.
* No need to set -offset left for .Bd literal.

ref.
https://git.suckless.org/slock/commit/ca6f30f621c1195b577ace7a14b9037fab0dab91.html

slock.1

@@ -1,5 +1,6 @@
-.Dd 2016-08-23
+.Dd October 6, 2023
 .Dt SLOCK 1
+.Os
 .Sh NAME
 .Nm slock
 .Nd simple X screen locker
@@ -9,31 +10,33 @@
 .Op Ar cmd Op Ar arg ...
 .Sh DESCRIPTION
 .Nm
-is a simple X screen locker. If provided,
-.Ar cmd Op Ar arg ...
+is a simple X screen locker.
+If provided,
+.Ar cmd
 is executed after the screen has been locked.
 .Sh OPTIONS
 .Bl -tag -width Ds
 .It Fl v
 Print version information to stdout and exit.
 .El
+.Sh EXAMPLES
+$
+.Nm
+/usr/sbin/s2ram
 .Sh SECURITY CONSIDERATIONS
 To make sure a locked screen can not be bypassed by switching VTs
 or killing the X server with Ctrl+Alt+Backspace, it is recommended
 to disable both in
 .Xr xorg.conf 5
 for maximum security:
-.Bd -literal -offset left
+.Bd -literal
 Section "ServerFlags"
 	Option "DontVTSwitch" "True"
 	Option "DontZap"      "True"
 EndSection
 .Ed
-.Sh EXAMPLES
-$
-.Nm
-/usr/sbin/s2ram
 .Sh CUSTOMIZATION
 .Nm
 can be customized by creating a custom config.h from config.def.h and
-(re)compiling the source code. This keeps it fast, secure and simple.
+(re)compiling the source code.
+This keeps it fast, secure and simple.