Merge pull request #2238 from Zexbe/chapter6tochapter18

Add note about chapter 18 in chapter 6

Author: steveklabnik

src/ch06-02-match.md

@@ -203,3 +203,8 @@ list before the `_` placeholder.
 
 However, the `match` expression can be a bit wordy in a situation in which we
 care about only *one* of the cases. For this situation, Rust provides `if let`.
+
+More about patterns, and matching can be found in [chapter 18][ch18-00-patterns].
+
+[ch18-00-patterns]:
+ch18-00-patterns