Add docs on multi-project pipelines mini graph

doc/ci/multi_project_pipeline_graphs.md

-# Multi-Project Pipeline Graphs
+# Multi-project pipeline graphs
 
 > [Introduced](https://gitlab.com/gitlab-org/gitlab-ee/issues/2121) in
 [GitLab Enterprise Edition Premium 9.3](https://about.gitlab.com/2017/06/22/gitlab-9-3-released/#multi-project-pipeline-graphs).
 
+When you set up [GitLab CI/CD](README.md) across multiple projects, you can visualize
+the entire pipeline, including all multi-project stages.
+
 ## Overview
 
 GitLab CI/CD is a powerful continuous integration tool built-in GitLab.
@@ -10,12 +13,14 @@ GitLab CI works not only per project, but also across projects. When you
 configure GitLab CI for your project, you can visualize the stages
 of your [jobs](pipelines.md#jobs) on a chart called [pipeline graph](pipelines.md#pipeline-graphs).
 
-When you set up [GitLab CI/CD](README.md) across multiple projects, you can visualize
-the entire pipeline, including all multi-project stages.
-
 ![Multi-project pipeline graph](img/multi_project_pipeline_graph.png)
 
-Multi-Project Pipeline Graphs are useful for larger projects, especially those
+For areas where the pipeline mini-graph is present, when hovering or clicking
+(mobile) they will expand and be shown next to each other.
+
+![Multi-project mini graph](img/multi_pipeline_mini_graph.gif)
+
+Multi-project pipeline graphs are useful for larger projects, especially those
 adopting a [microservices architecture](https://about.gitlab.com/2016/08/16/trends-in-version-control-land-microservices/),
 that often have a set of interdependent components which form the complete product.
 
@@ -24,7 +29,7 @@ that often have a set of interdependent components which form the complete produ
 Let's assume you deploy your web app from different projects in GitLab:
 
 - One for the free version, which has its own pipeline that builds and tests your app
-- One for the paid version adds-ons, which also pass through builds and tests
+- One for the paid version add-ons, which also pass through builds and tests
 - One for the documentation, which also builds, tests, and deploys with an SSG
 
 With Multi-Project Pipeline Graphs, you can visualize the entire pipeline in a

doc/ci/pipelines.md

@@ -186,9 +186,9 @@ by name. The order of severity is:
 
 ![Pipeline mini graph sorting](img/pipelines_mini_graph_sorting.png)
 
-### Multi-Project Pipelines Graphs
+### Multi-project pipelines graphs
 
-With [Multi-Project Pipeline Graphs](multi_project_pipeline_graphs.md),
+With [multi-project pipeline graphs](multi_project_pipeline_graphs.md),
 you can visualize cross-project pipelines.
 
 It is available only in [GitLab Enterprise Edition Premium][eep].