Update CONTRIBUTING.md

Co-authored-by: Alex Batisse <alexandre.batisse@hey.com>

CONTRIBUTING.md

@@ -81,7 +81,9 @@ The documentation is formed by a series of markdown files located in directory [
 This means that, to modify the [API reference](https://robaina.github.io/Pynteny/references/api/), all you need to do is to modify the docstring directly in the source file where the definion/class is located. And, to update the documentation pages, you just have to update the corresponding markdown file in the [docs](https://github.com/Robaina/Pynteny/tree/main/docs) directory. Note that, if you need to change the documentation structure (e.g., add or new pages),you would need to tell mkdocs about this change through its [configuration file](https://github.com/Robaina/Pynteny/blob/main/mkdocs.yml). Or just open an issue and ask for help!
 
 When all the changes are ready to deploy, just open a pull request. After reviewing and merging the changes, the documentation will be automatically deployed.
+Run the documentation locally with:
 
+> mkdocs serve
 ## Tests on push and pull request to main
 
 Pynteny's repo contains a [GitHub Action](https://github.com/features/actions) to perform build and integration tests which is triggered automatically on push and pull request events to the main brach. Currently the tests include building and installing Pynteny in Ubuntu and MacOS and running the [test](tests) suit.