Merge branch 'docs/how-to-develop-for-dot-gitlab-folder' into 'master'

Adds docs about file and folders names used in .gitlab

See merge request gitlab-org/gitlab!42090

doc/development/README.md

@@ -197,6 +197,7 @@ See [database guidelines](database/index.md).
 - [Defining relations between files using projections](projections.md)
 - [Reference processing](./reference_processing.md)
 - [Compatibility with multiple versions of the application running at the same time](multi_version_compatibility.md)
+- [Features inside `.gitlab/`](./features_inside_dot_gitlab.md)
 
 ## Other GitLab Development Kit (GDK) guides
 

doc/development/features_inside_dot_gitlab.md

+# Features inside the `.gitlab/` directory
+
+We have implemented standard features that depend on configuration files in the `.gitlab/` directory. You can find `.gitlab/` in various GitLab repositories.
+When implementing new features, please refer to these existing features to avoid conflicts:
+
+- [Custom Dashboards](../operations/metrics/dashboards/index.md#add-a-new-dashboard-to-your-project): `.gitlab/dashboards/`.
+- [Issue Templates](../user/project/description_templates.md#creating-issue-templates): `.gitlab/issue_templates/`.
+- [Merge Request Templates](../user/project/description_templates.md#creating-merge-request-templates): `.gitlab/merge_request_templates/`.
+- [GitLab Kubernetes Agents](https://gitlab.com/gitlab-org/cluster-integration/gitlab-agent/-/blob/master/doc/configuration_repository.md#layout): `.gitlab/agents/`.
+- [CODEOWNERS](../user/project/code_owners.md#how-to-set-up-code-owners): `.gitlab/CODEOWNERS`.
+- [Route Maps](../ci/review_apps/#route-maps): `.gitlab/route-map.yml`.
+- [Customize Auto DevOps Helm Values](../topics/autodevops/customize.md#customize-values-for-helm-chart): `.gitlab/auto-deploy-values.yaml`.
+- [GitLab managed apps CI/CD](../user/clusters/applications.md#usage): `.gitlab/managed-apps/config.yaml`.
+- [Insights](../user/project/insights/index.md#configure-your-insights): `.gitlab/insights.yml`.
+- [Service Desk Templates](../user/project/service_desk.md#using-customized-email-templates): `.gitlab/service_desk_templates/`.
+- [Web IDE](../user/project/web_ide/#web-ide-configuration-file): `.gitlab/.gitlab-webide.yml`.