uploads: show videos and ugoiras on upload page.

* On the upload page, show the video when uploading a video or ugoira.
* On the upload page, show the filesize and resolution beneath the
  image, instead of above it.
* On the media asset show page, show the full video or ugoira instead of
  just the thumbnail.

app/components/media_asset_component.rb

@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+# A component for showing a full-sized image or video for a media asset.
+class MediaAssetComponent < ApplicationComponent
+  attr_reader :media_asset
+
+  delegate :image_width, :image_height, :variant, :is_image?, :is_video?, :is_ugoira?, :is_flash?, to: :media_asset
+
+  def initialize(media_asset:)
+    super
+    @media_asset = media_asset
+  end
+end