Add ContextMenuBuilder argument for searching using DuckDuckGo instead of Google

[Powersource]

I don't know if this code works since I wasn't able to run the example :sweat_smile:. And the tests don't all work but they didn't for me even before I started coding hehe. So would be good if someone could try this out before potentially merging :)

[Powersource]

So I added this directly in the app instead using the processMenu function here https://github.com/ssbc/patchwork/pull/980 But it would still be cool to have this PR merged :)