Declaring a custom namespace extension for Buckshot Templates

gistfile1.xml

<!-- 
  In addition to the default namespace, we add another named namespace
  which declares that anything prefixed with 'custom' should be part of
  that namespace scope.
-->
<template xmlns='http://buckshotui.org/platforms/html'
          xmlns:custom='http://buckshotui.org/sprockets'>
  <!-- elements in the default namespace work just fine. -->
  <stack>
    <textblock text='Here is that sprocket that you ordered:' />
    <custom:sprocket teeth='12' diameter='25cm' />
  </stack>
</template>