Onboarding welcome page

- Add styles for blue popovers
- Add render_if_exists to help menu for "Learn GitLab" menu item

app/assets/stylesheets/components/popover.scss

@@ -10,6 +10,26 @@
       color: $gray-600;
     }
   }
+
+  &.blue {
+    background-color: $blue-600;
+
+    .popover-body {
+      color: $white-light;
+    }
+
+    &.bs-popover-bottom {
+      .arrow::after {
+        border-bottom-color: $blue-600;
+      }
+    }
+
+    &.bs-popover-top {
+      .arrow::after {
+        border-top-color: $blue-600;
+      }
+    }
+  }
 }
 
 .mr-popover {
@@ -18,3 +38,16 @@
     line-height: 1.33;
   }
 }
+
+.onboarding-welcome-page {
+  .popover {
+    min-width: auto;
+    max-width: 40%;
+
+    .popover-body {
+      padding-top: $gl-padding;
+      padding-bottom: $gl-padding;
+      font-size: $gl-font-size-small;
+    }
+  }
+}

app/views/layouts/header/_help_dropdown.html.haml

@@ -2,6 +2,7 @@
   - if current_user_menu?(:help)
     %li
       = link_to _("Help"), help_path
+    = render_if_exists "shared/learn_gitlab_menu_item"
     %li.divider
   %li
     = link_to _("Submit feedback"), "https://about.gitlab.com/submit-feedback"