Add public layout component based layout template

Uses the public layout component[1] to add a constrained width and a full width
layout template.

Dependent on Slimmer having compatibility added [2].

[1]: https://components.publishing.service.gov.uk/component-guide/layout_for_public
[2]: alphagov/slimmer#265

app/controllers/root_controller.rb

@@ -23,6 +23,8 @@ class RootController < ApplicationController
     503
     504
     campaign
+    gem_layout
+    gem_layout_full_width
     scheduled_maintenance
     print
     proposition_menu

app/views/root/_error_page.html.erb

@@ -3,7 +3,7 @@
   <%= stylesheet_link_tag "error-page-print", media: "print" %>
 <% end %>
 
-<% if @emergency_banner then
+<% if @emergency_banner
     emergency_banner = render "components/emergency_banner", {
       campaign_class: @emergency_banner.campaign_class,
       heading: @emergency_banner.heading,

app/views/root/_gem_base.html.erb

@@ -0,0 +1,45 @@
+<% if @emergency_banner
+    emergency_banner = render "components/emergency_banner", {
+      campaign_class: @emergency_banner.campaign_class,
+      heading: @emergency_banner.heading,
+      link: @emergency_banner.link,
+      link_text: @emergency_banner.link_text,
+      short_description: @emergency_banner.short_description,
+    }
+  end
+  user_satisfaction_survey = '<div id="user-satisfaction-survey-container"></div>'
+  global_bar = render "components/global_bar"
+%>
+
+<%= render "govuk_publishing_components/components/layout_for_public", {
+  emergency_banner: emergency_banner,
+  full_width: full_width,
+  global_bar: user_satisfaction_survey + global_bar,
+  navigation_items: [
+  {
+    text: "Account",
+    href: Plek.new.find("account-manager"),
+    data: {
+      module: "explicit-cross-domain-links",
+      link_for: "accounts-signed-in",
+    },
+  },
+  {
+    text: "Sign out",
+    href: Plek.new.website_root + "/transition-check/logout",
+    data: {
+      module: "explicit-cross-domain-links",
+      link_for: "accounts-signed-in",
+    },
+  },
+  {
+    text: "Sign in",
+    href: Plek.new.website_root + "/transition-check/login",
+    data: {
+      module: "explicit-cross-domain-links",
+      link_for: "accounts-signed-out",
+    },
+  }],
+  title: content_for?(:title) ? yield(:title) : "GOV.UK - The best place to find government services and information",
+
+} %>

app/views/root/gem_layout.html.erb

@@ -0,0 +1,3 @@
+<%= render partial: "gem_base", locals: {
+  full_width: false,
+} %>

app/views/root/gem_layout_full_width.html.erb

@@ -0,0 +1,3 @@
+<%= render partial: 'gem_base', locals: {
+  full_width: true,
+} %>