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

config/locales/io.yml

@@ -3,23 +3,12 @@ io:
   about:
     about_mastodon: Mastodon esas <em>gratuita, apertitkodexa</em> sociala reto. Ol esas <em>sencentra</em> altra alternativo a komercala servadi. Ol evitigas, ke sola firmo guvernez tua tota komunikadol. Selektez servero, quan tu fidas. Irge qua esas tua selekto, tu povas komunikar kun omna altra uzeri. Irgu povas krear sua propra instaluro di Mastodon en sua servero, e partoprenar en la <em>sociala reto</em> tote glate.
     about_this: Pri ta instaluro
-    apps: Apliki
     business_email: 'Profesionala retpost-adreso:'
     closed_registrations: Membresko ne nun esas posible en ta instaluro.
     contact: Kontaktar
     description_headline: Quo esas %{domain}?
     domain_count_after: altra instaluri
     domain_count_before: Konektita ad
-    features:
-      api: Apertita API por apliki e servadi
-      blocks: Kompleta utensili por blokusar e celar
-      characters: Til 500 signi por singla mesajo
-      chronology: Tempolinei seguntempa
-      ethics: 'Etike kreita: nula anunco, nula trakado'
-      gifv: Posibleso diskononigar mikra videi e GIFV
-      privacy: Videbleso ajustita segun la mesajo
-      public: Publika tempolinei
-    features_headline: Quale Mastodon esas diferanta
     get_started: Komencar
     links: Ligili
     other_instances: Altra instaluri
@@ -146,8 +135,6 @@ io:
           desc_html: Displayed on frontpage when registrations are closed<br>You can use HTML tags
           title: Closed registration message
         open:
-          disabled: Disabled
-          enabled: Enabled
           title: Open registration
       setting: Setting
       site_description: