Add a pcase-let example to the manual

* doc/lispref/control.texi (Destructuring with pcase Patterns):
Add a pcase-let example.

doc/lispref/control.texi

@@ -1283,6 +1283,15 @@ bindings that can then be used inside @var{body}.  The variable
 bindings are produced by destructuring binding of elements of
 @var{pattern} to the values of the corresponding elements of the
 evaluated @var{exp}.
+
+Here's a trivial example:
+
+@example
+(pcase-let ((`(,major ,minor)
+	     (split-string "image/png" "/")))
+  minor)
+     @result{} "png"
+@end example
 @end defmac
 
 @defmac pcase-let* bindings body@dots{}