Allow the user to search the settings

[tdulcet]

The respective Firefox and Thunderbird about:preferences settings pages allow the user to search the settings:

For extensions like Server Status with lots of options, it would be very helpful if this library had a similar search functionality so users could search the options page to quickly find the specific option they wanted. Similar to the reset button, I believe this is a feature most extensions could use.

This library already includes a search.js file that implements a search for the documentation. It could potenchally be reused for the options page.