Fix blurhash and autoplay not working on public pages (#11585)

app/controllers/home_controller.rb

app/controllers/public_timelines_controller.rb

app/controllers/shares_controller.rb

app/controllers/tags_controller.rb

app/helpers/application_helper.rb

app/serializers/initial_state_serializer.rb

app/views/home/index.html.haml

app/views/layouts/public.html.haml

app/views/public_timelines/show.html.haml

app/views/shares/show.html.haml

app/views/tags/show.html.haml

spec/controllers/home_controller_spec.rb

spec/controllers/shares_controller_spec.rb