I am loving this extension! Just wondering if you could add a user page or something where users can submit more examples (If something like this already exists, please let me know!)? A couple of things I'm looking for but haven't figured out just yet are how to have the selected text's hyperlinked url open as cached link [basically launch url as a google webcache search] or similarly open link as viewsource. Hope that somehow makes sense.
Here's some dumb ones I use regularly, lol, if anyone cares. :D

Audible:
https://www.audible.com/search?keywords={searchTerms}
Goodreads:
https://www.goodreads.com/search?utf8=%E2%9C%93&query={searchTerms}
Google Dictionary:
https://www.google.com/search?hl=en&q=define%20{searchTerms}
Google Playstore:
https://play.google.com/store/search?q={searchTerms}&c=apps
Google Site:
https://www.google.com/search?q={searchTerms}%20site:{hostname}
Google Images:
https://www.google.com/search?tbm=isch&q={searchTerms}&tbs=imgo:1
DuckDuckGo:
https://duckduckgo.com/?q={searchTerms}&kae=d&kl=us-en&kad=en_US&kp=-2&kz=-1&kn=1&k1=-1&kaj=u&kam=google-maps&kv=l&kak=-1&kax=-1&kaq=-1&kap=-1&kao=-1&kac=-1&ks=l&kw=w&km=m&k5=1&kt=c
DuckDuckGo Images:
https://duckduckgo.com/?q={searchTerms}&kp=-2&kaj=u&kam=google-maps&kau=-1&kao=-1&kaq=-1&kap=-1&kax=-1&ks=l&kw=w&kae=d&k5=-1&kav=1&t=h_&iax=images&ia=images

In any event, the app is awesome. Highly recommend!