Add imports for the Synom::description example
diff --git a/src/synom.rs b/src/synom.rs
index b53cdb6..f631f8b 100644
--- a/src/synom.rs
+++ b/src/synom.rs
@@ -176,7 +176,10 @@
     ///
     /// # Examples
     ///
-    /// ```ignore
+    /// ```
+    /// # use syn::buffer::Cursor;
+    /// # use syn::synom::{Synom, PResult};
+    /// #
     /// struct ExprForLoop {
     ///     // ...
     /// }