[Feature Request] Add DuckDuckGo as an upstream search engine

[305a385]

I noticed that there aren't many upstream search engines. In fact the only search engine for text search is google! (if I read this source code right)

Pros:

• Google ratelimits VPSs. which can lead to issues such as text not showing (see #226); a second option for text searches could help workaround this
• More search engines = more results :), this is pretty self explanatory
• If you have your tinfoil hat on real tight, you could remove google as an upstream and still get text results

Info that might help with implementation:

Duckduckgo has an API but it only works for text

[hnhx]

From my experience DDG has horrible text results so thats why i didnt bother with it. I might implement in support for it as a fallback when Google blocks an instance though.