[doc] update the contributing guide

add instructions for code linting with  pre-commit

CONTRIBUTING.md

@@ -15,3 +15,28 @@ do it again.
 
 All submissions, including submissions by project members, require review. We use GitHub pull requests for this purpose. Consult
 [GitHub Help](https://help.github.com/articles/about-pull-requests/) for more information on using pull requests.
+
+## Code linting
+
+We use a pre-commit hook to clean/format code before submitting a change. This allows for a cleaner code base. pre-commit will fetch and trigger the
+_prettier_ and _markdown_ link tools and run it through your staged files.
+
+Install pre-commit on your cloud top
+
+```shell
+sudo apt install pre-commit
+```
+
+Then install the git hook :
+
+```shell
+pre-commit install
+```
+
+you can also run pre-commit on all the files manually before committing your changes :
+
+```shell
+pre-commit run --all-files
+```
+
+more information about pre-commit : <https://pre-commit.com/>