Add screenshots to GitLab Trusted Publishing docs

Author: facutuesca

docs/user/assets/trusted-publishing/gitlab/pending-publisher-form-filled.png

@@ -111,7 +111,7 @@ each.
     that uses a publishing workflow defined in `release.yml` and a custom
     environment named `release`, then you'd do the following:
 
-    TODO: insert screenshot here
+    ![](/assets/trusted-publishing/gitlab/project-publishing-form.png)
 
     !!! note
 
@@ -123,7 +123,7 @@ each.
     Once you click "Add", your publisher will be registered and will appear
     at the top of the page:
 
-    TODO: insert screenshot here
+    ![](/assets/trusted-publishing/gitlab/project-publisher-registered.png)
 
     From this point onwards, the `release.yml` workflow on `namespace/sampleproject`
     will be able to generate short-lived API tokens from PyPI for the project you've

docs/user/assets/trusted-publishing/gitlab/pending-publisher-registered.png

@@ -71,7 +71,7 @@ provide the name of the PyPI project that will be created.
     `release.yml` and an environment named `release` that you would like to publish
     to PyPI as `sampleproject`, then you would do the following:
 
-    TODO: add screenshot
+    ![](/assets/trusted-publishing/gitlab/pending-publisher-form-filled.png)
 
     !!! note
 
@@ -80,7 +80,7 @@ provide the name of the PyPI project that will be created.
 
     Clicking "Add" will register the "pending" publisher, and show it to you:
 
-    TODO: add screenshot
+    ![](/assets/trusted-publishing/gitlab/pending-publisher-registered.png)