Make the example spreadsheet scroll horizontally

This replicates how we let large spreadsheets scroll horizontally.

Pro: this looks nicer and is more usable

Con: the code for this feels a bit fragile, especially the calling of
`.maintainWidth` twice, ie as many times as a it takes to get stuff to
render properly.

app/templates/views/send.html

@@ -29,7 +29,8 @@
     <acronym title="Open Document Spreadsheet">ODS</acronym>,
     or Microsoft Excel spreadsheet
   </p>
-  <div class="spreadsheet">
+
+  <div class="spreadsheet" data-module="fullscreen-table">
     {% call(item, row_number) list_table(
       example,
       caption="Example",