look(1): Add EXAMPLES section

Add two simple examples. In this case I opted to show a small portion of
the output since it helps to understand what the tool does. It shows the use
of the -t flag too.

PR:
Submitted by:
Reported by:
Reviewed by:	gbe@
Approved by:	manpages (bcr@)
Obtained from:
MFC after:
MFH:
Relnotes:
Security:
Sponsored by:
Differential Revision:	https://reviews.freebsd.org/D27543

usr.bin/look/look.1

@@ -28,7 +28,7 @@
 .\"     @(#)look.1	8.1 (Berkeley) 6/14/93
 .\" $FreeBSD$
 .\"
-.Dd July 17, 2004
+.Dd December 29, 2020
 .Dt LOOK 1
 .Os
 .Sh NAME
@@ -96,6 +96,35 @@ The
 .Nm
 utility exits 0 if one or more lines were found and displayed,
 1 if no lines were found, and >1 if an error occurred.
+.Sh EXAMPLES
+Look for lines starting with
+.Ql xylene
+in the file
+.Pa /usr/share/dict/words :
+.Bd -literal -offset indent
+$ look xylen
+xylene
+xylenol
+xylenyl
+.Ed
+.Pp
+Same as above, but do not consider any characters in
+.Ar string
+beyond the first
+.Ql e .
+Note that
+.Fl f
+is implicit since we are searching the default file
+.Pa /usr/share/dict/words :
+.Bd -literal -offset indent
+$ look -t e xylen
+Xyleborus
+xylem
+xylene
+xylenol
+xylenyl
+xyletic
+.Ed
 .Sh COMPATIBILITY
 The original manual page stated that tabs and blank characters participated
 in comparisons when the