Bug 23304: (follow-up) Add markup structure comments

Bug 23304: (follow-up) Add markup structure comments

This patch adds comments to the template to highlight the markup
structure. It also removes the obsolete "type" attribute from the
<script> tag.

This patch should have no effect on the interface or functionality.

Signed-off-by: Nadine Pierre <nadine.pierre@inLibro.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
(cherry picked from commit b76aa551049edcb1575d8a4cce917cbc0eb8fa24)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>