Add speaker note about returning values from loop

src/control-flow-basics/loops/loop.md

@@ -21,4 +21,9 @@ fn main() {
 - The `loop` statement works like a `while true` loop. Use it for things like
   servers which will serve connections forever.
 
+## More to Explore
+
+- `loop` is the only form of loop that can return a value. If students are
+  curious, demonstrate breaking with a value, e.g. `break x + 10`.
+
 </details>