[Koha] Add new option to OPAC user menu

[Vitor Fernandes]

Hello.

I've added an new option in the OPAC user menu where the user can
change his reading preferences. The reading preferences is a custom
attribute created for the effect.

The problem is that the OPAC uses Javascript to change the interface,
but when the user select the new option reading preferences the all
page is reload.
I know that the problem is that I'm not using Javascript to do the
page change, but I don't know where and which JavaScript file I need
to change.

Thanks for your time.

Regards.
Vitor Fernandes