Merge branch 'add-pgformatter-into-database-tooling-docs' into 'master'

Add pgFormatter as a database tooling

See merge request gitlab-org/gitlab-ce!30374

doc/development/README.md

@@ -82,6 +82,7 @@ description: 'Learn how to contribute to GitLab.'
 - [Understanding EXPLAIN plans](understanding_explain_plans.md)
 - [explain.depesz.com](https://explain.depesz.com/) for visualising the output
   of `EXPLAIN`
+- [pgFormatter](http://sqlformat.darold.net/) a PostgreSQL SQL syntax beautifier
 ### Migrations