#3506040 Add $DRUPAL_PROJECTS_PATH variable and remove hard-coded paths

Closes #3506040

docs/info/customizations.md

@@ -125,6 +125,17 @@ variables:
   PROJECT_NAME: 'my_project'
 ```
 
+## Projects Path
+
+The path within the Drupal installation to the project being tested will default to `modules/custom`, `themes/custom` or `profiles/custom` depending on the project type. The equivalent path for Drupal 7 testing is `sites/all/modules/custom` etc.
+
+If this is not the path you want, you can change it by defining a value for the `$DRUPAL_PROJECTS_PATH` variable. For example:
+
+```
+variables:
+  DRUPAL_PROJECTS_PATH: 'modules/contrib'
+```
+
 ## Workflow
 
 The [workflow](https://docs.gitlab.com/ee/ci/yaml/workflow.html) of a repository defines when pipelines will be run. Various events, such as creating a Merge Request, committing to the default branch or submitting via the pipeline UI can be used in combinations of rules, and if any of the conditions are true then the pipeline will be run. Gitlab Templates defines a [default workflow](https://git.drupalcode.org/project/gitlab_templates/-/blob/main/includes/include.drupalci.workflows.yml) which in most cases will be exactly what your project needs. However, if you do need to extend this default workflow, you can use the following: