Document how to run the wrap valídator. [skip ci]

docs/markdown/Adding-new-projects-to-wrapdb.md

@@ -252,10 +252,16 @@ to functionality. All such changes must be submitted to upstream. You
 may also host your own Git repo with the changes if you wish. The Wrap
 system has native support for Git subprojects.
 
-## Reviewing wraps
+## Passing automatic validation
 
-See [Wrap review guidelines](Wrap-review-guidelines.md), especially
+Every submitted wrap goes through an automated correctness review and
-the part about tooling that you can use to check for the most common
+passing it is a requirement for merging. Therefore it is highly
-problems yourself. Fixing all issues reported by the tool is a
+recommended that you run the validation checks yourself so you can fix
-mandatory requirement for getting your MR accepted, so doing this
+any issues faster.
-proactively makes the review process smoother.
+
+Instructions on how to install and run the review tool can be found on
+the [Wrap review guidelines page](Wrap-review-guidelines.md).  If your
+submission is merge request number 5 for a repository called `mylib`,
+then you'd run the following command:
+
+    mesonwrap review --pull-request 5 mylib