update README.md

Author: keiravillekode

README.md

@@ -22,5 +22,7 @@ When adding a new exercise, ensure that the exercise is included in the `exercis
 
 Run `prove -re raku exercises/practice/*/.meta/solutions/` to run all exercise tests.
 
+Run `bin/verify-exercises-in-docker` to run tests in the track's test runner Docker image.
+
 ### Raku icon
 The Raku "Camelia" logo is owned by Larry Wall and is released under version 2.0 of the Artistic License. We are using it to identify the Raku language itself, not any part of Exercism, which we believe to be admissible under fair use. The version of the logo that we are using is an adaptation of the logo found on <https://en.wikipedia.org/wiki/Raku_(programming_language)>.