Allow opensearch to use current browser search engine

[Malvoz]

Many websites do not implement their own search function, however it is possible to let an external url template power opensearch.

You could let the url template use a search engine of choice like this:
https://aaronparecki.com/2011/07/11/3/how-to-let-google-power-opensearch-on-your-website

However, the search engine that the web authors specifies may not be that of the users preference. If sites can opt-in to allow an opensearch description to use the users current browser to power the search function it could serve as an easy integration for opensearch for all web authors.