New images for GitLab basics "Create MR" docs

doc/gitlab-basics/add-merge-request.md

 # How to create a merge request
 
-Merge Requests are useful to integrate separate changes that you've made to a project, on different branches.
+Merge requests are useful to integrate separate changes that you've made to a
+project, on different branches. This is a brief guide on how to create a merge
+request. For more information, check the
+[merge requests documentation](../user/project/merge_requests.md).
 
-To create a new Merge Request, sign in to GitLab.
+---
 
-Go to the project where you'd like to merge your changes:
+1. Before you start, you should have already [created a branch](create-branch.md)
+   and [pushed your changes](basic-git-commands.md) to GitLab.
 
-![Select a project](img/select_project.png)
+1. You can then go to the project where you'd like to merge your changes and
+   click on the **Merge requests** tab.
 
-Click on "Merge Requests" on the left side of your screen:
+    ![Merge requests](img/project_navbar.png)
 
-![Merge requests](img/merge_requests.png)
+1. Click on **New merge request** on the right side of the screen.
 
-Click on "+ new Merge Request" on the right side of the screen:
+    ![New Merge Request](img/merge_request_new.png)
 
-![New Merge Request](img/new_merge_request.png)
+1. Select a source branch and click on the **Compare branches and continue** button.
 
-Select a source branch or branch:
+    ![Select a branch](img/merge_request_select_branch.png)
 
-![Select a branch](img/select_branch.png)
+1. At a minimum, add a title and a description to your merge request. Optionally,
+   select a user to review your merge request and to accept or close it. You may
+   also select a milestone and labels.
 
-Click on the "compare branches" button:
+    ![New merge request page](img/merge_request_page.png)
 
-![Compare branches](img/compare_branches.png)
-
-Add a title and a description to your Merge Request:
-
-![Add a title and description](img/title_description_mr.png)
-
-Select a user to review your Merge Request and to accept or close it. You may also select milestones and labels (they are optional). Then click on the "submit new Merge Request" button:
-
-![Add a new merge request](img/add_new_merge_request.png)
-
-Your Merge Request will be ready to be approved and published.
-
-### Note
-
-After you created a new branch, you'll immediately find a "create a Merge Request" button at the top of your screen.
-You may automatically create a Merge Request from your recently created branch when clicking on this button:
-
-![Automatic MR button](img/button-create-mr.png)
+1. When ready, click on the **Submit merge request** button. Your merge request
+   will be ready to be approved and published.