Update submissions.js to support "details" parameter of {{Afc decline}}.

Support "details" parameter of {{Afc decline}}.

A recent change started supporting the "reason" tag in {{Afc decline}}, but this didn't work with reasons such as a custom reason or the "dup" reason that require a second parameter. I have changed {{Afc decline}} to support a "details" parameter that passes a second parameter to {{AFC submission/comments}}. This parameter is already collected by the AFCH script for use in {{AFC submission}}, but needs to be passed to {{Afc decline}} as well.

As a disclaimer, I haven't tested this patch.
Very minor nitpick, could you change this to `newParams['3'] || ''` instead? Just for the sake of keeping consistent style throughout the project.