doc/tutorial/basics: include commands to run

To give the user a clue on how to get the output.

Change-Id: I2fb92d08599c95b7b1cbd70e8f41d2760e359c14
Reviewed-on: https://cue-review.googlesource.com/c/1580
Reviewed-by: Marcel van Lohuizen <mpvl@google.com>
diff --git a/doc/tutorial/basics/fold.md b/doc/tutorial/basics/fold.md
index 952c240..cb1eb0d 100644
--- a/doc/tutorial/basics/fold.md
+++ b/doc/tutorial/basics/fold.md
@@ -7,11 +7,13 @@
 CUE allows a shorthand for structs with single members.
 
 <!-- CUE editor -->
+_fold.cue:_
 ```
 outer middle inner: 3
 ```
 
 <!-- JSON result -->
+`$ cue export fold.cue`
 ```json
 {
     "outer": {