add screenshots

pages/pipelines/dashboard_walkthrough.md

@@ -68,8 +68,12 @@ Clicking through to a pipeline page shows the [build history](#build-history) fo
 
 You can filter a pipeline’s builds by branch, build state, or your own builds using the Filter menu.
 
+<%= image "filtering-builds.png", width: 2824/2, height: 1432/2, alt: "Screenshot of the builds filter menu" %>
+
 To see the steps for a build, click the Show steps button on the right of any build.
 
+<%= image "showing-build-steps.png", width: 2552/2, height: 964/2, alt: "Screenshot of toggling build steps" %>
+
 ## Build page
 
 Clicking through to a build page shows the full list of jobs and other steps in that build, the information about who triggered the build, and the controls for rebuilding or cancelling the build while it's in progress.