Refutability: Mention let-else statement

src/ch18-02-refutability.md

@@ -10,11 +10,11 @@ a_value` because if the value in the `a_value` variable is `None` rather than
 
 Function parameters, `let` statements, and `for` loops can only accept
 irrefutable patterns, because the program cannot do anything meaningful when
-values don’t match. The `if let` and `while let` expressions accept
-refutable and irrefutable patterns, but the compiler warns against
-irrefutable patterns because by definition they’re intended to handle possible
-failure: the functionality of a conditional is in its ability to perform
-differently depending on success or failure.
+values don’t match. The `if let` and `while let` expressions and the
+`let`-`else` statement accept refutable and irrefutable patterns, but the
+compiler warns against irrefutable patterns because by definition they’re intended
+to handle possible failure: the functionality of a conditional is in its ability
+to perform differently depending on success or failure.
 
 In general, you shouldn’t have to worry about the distinction between refutable
 and irrefutable patterns; however, you do need to be familiar with the concept