Add collection_id filter to searchbar shortcode

Hi, thanks for this plugin! We are implementing this solution on our websites, and most of it seems to work flawlessly so far.

However, one of the business request seemed not to be available. We are a research foundation and have several teams working of different projects. Our Zotero repository is divided by collections, and each team want to display a searchbar to search only in its collection. So we needed a filter for that in the searchbar shortcode.

But by digging in the code, I found a quite easy way to implement that. Just by adding the line

zpSearchBarParams += "&collection_id="+jQuery(".ZP_COLLECTION_ID").text();

In js/zotpress.lib.searchbar.js line 45, it seems that it’s now working and taking into account the collection_id parameter from the shortcode.

So we wonder if you would consider adding this in a future version ?