Redesign the landing page, mount public timeline on it (#4122)

* Redesign the landing page, mount public timeline on it

* Adjust the standalone mounted component to the lacking of router

* Adjust auth layout pages to new design

* Fix tests

* Standalone public timeline polling every 5 seconds

* Remove now obsolete translations

* Add responsive design for new landing page

* Address reviews

* Add floating clouds behind frontpage form

* Use access token from public page when available

* Fix mentions and hashtags links, cursor on status content in standalone mode

* Add footer link to source code

* Fix errors on pages that don't embed the component, use classnames

* Fix tests

* Change anonymous autoPlayGif default to false

* When gif autoplay is disabled, hover to play

* Add option to hide the timeline preview

* Slightly improve alt layout

* Add elephant friend to new frontpage

* Display "back to mastodon" in place of "login" when logged in on frontpage

* Change polling time to 3s

app/controllers/about_controller.rb

@@ -4,7 +4,10 @@ class AboutController < ApplicationController
   before_action :set_body_classes
   before_action :set_instance_presenter, only: [:show, :more, :terms]
 
-  def show; end
+  def show
+    serializable_resource = ActiveModelSerializers::SerializableResource.new(InitialStatePresenter.new(initial_state_params), serializer: InitialStateSerializer)
+    @initial_state_json   = serializable_resource.to_json
+  end
 
   def more; end
 
@@ -15,6 +18,7 @@ class AboutController < ApplicationController
   def new_user
     User.new.tap(&:build_account)
   end
+
   helper_method :new_user
 
   def set_instance_presenter
@@ -24,4 +28,11 @@ class AboutController < ApplicationController
   def set_body_classes
     @body_classes = 'about-body'
   end
+
+  def initial_state_params
+    {
+      settings: {},
+      token: current_session&.token,
+    }
+  end
 end