Add the Option for a Whitelist

[thekief]

Is your feature request related to a problem? Please describe.

I mainly use the addon for specific sites that contain a bulk of information that I need to go through. The number of websites I use this plugin for is much, much smaller than the number of sites the plugin I would like to disable it for.

Describe the solution you'd like

In addition to blacklisting, it should be possible to choose and create a whitelist that enables the plugin only on certain sites.

Describe alternatives you've considered

Firefox is currently looking into restricting plugins to certain websites but there is no ETA yet.

Additional context

n/a