feat: build tooltip text for assets

Author: ElliottAYoung

app/cells/plugins/core/asset/input.haml

@@ -7,3 +7,6 @@
 = render_field_id
 = render_label
 = render_input
+- if @options[:tooltip]
+  %br
+    = render_tooltip

app/cells/plugins/core/asset_cell.rb

@@ -39,6 +39,10 @@ def render_input
         @options[:form].file_field 'data[asset]'
       end
 
+      def render_tooltip
+        @options[:tooltip]
+      end
+
       def associated_content_item_thumb_url
         data['asset']['style_urls']['mini']
       end