Update result.md (google#250)

* Update result.md

Adding a speaker note that `Result` documentation is a recommended read.

* Adding a note why `Result` encourages error checking.

* Wordsmithing

Co-authored-by: Andrew Walbran <qwandor@google.com>

Author: 2 people

src/error-handling/result.md

@@ -21,3 +21,13 @@ fn main() {
     }
 }
 ```
+
+<details>
+
+  * As with `Option`, the successful value sits inside of `Result`, forcing the developer to
+    explicitly extract it. This encourages error checking. In the case where an error should never happen,
+    `unwrap()` or `expect()` can be called, and this is a signal of the developer intent too.  
+  * `Result` documentation is a recommended read. Not during the course, but it is worth mentioning. 
+    It contains a lot of convenience methods and functions that help functional-style programming. 
+    
+</details>