Do not search for DOIs & ISBNs in certain areas on specific webpage

There are multiple clients that are not happy about Alternatives popup showing on certain webpages, related to DOIs and ISBNs found on the webpage area that should not be looked at.

One example is Wikipedia, where Alternatives popup shows most of the time. It picks up DOIs and ISBNs mostly from the Reference are and it's (by the client) not related to the content itself.

Proposed solution is to tell extension which DOM elements to exclude from the search on certain (popular) websites.

Here are few tickets where client requested this functionality:
https://techfromsage.atlassian.net/browse/LL-4085
https://techfromsage.atlassian.net/browse/LL-4090